Concepts in
Chemistry
CHAPTER-IV
TRIVIAL OR COMMON SYSTEM OF NOMENCLATURE
Naming an organic compound on the basis of the rules recommended by IUPAC is
absolutely essential for big and complex molecules. However, small molecules are more popularly
addressed by their common names or the trivial or the primitive names. We already know before
that IUPAC has accepted a few common names as official names e.g acetic acid, formic acid
etc. for some compounds and isopropyl, sec-butyl, tert-butyl etc. as some groups. A detailed
logically genesis of the common system is discussed below.
TYPES OF CARBON ATOMS:
There are four types of carbon atoms.
(i) Primary or 10 carbon atom:
(ii) Secondary(sec-) or 20 carbon atom:
(iii) Tertiary(tert-) or 30 carbon atom:
(iv) Quaternary or 40 carbon atom:
carbon atom attached with 3 or 4 H atoms.
carbon atom attached with 2 H atoms.
carbon atom attached with 1 H atom
carbon atom attached with no H atom.
1
1
Example:
0
H3 C
0
1
CH3
0
3
CH
0
CH3
4
0
C
0
1
2
0
CH2
1 CH
3
0
3
CH
0
CH3
1
0
CH3
In the above example, all the carbon atoms have been assigned with their types.
SAQ IV.1. (i)Name the molecule in which a primary carbon atoms is linked with 4 H
atom.
(ii)Draw the structure and give the IUPAC name of the compound which contains one 40
and four 10 carbon atoms.
TYPES OF ALKYL GROUPS:
In common system alkyl groups are prefixed with the symbols n-, iso, sec-, tert- and neo. While
naming the alkyl group all the carbon atoms present in the alkyl group are counted. Numbering of
carbon atoms is not done in this case like IUPAC system.
(i)
normal or n-alkyl group: If all the carbon atoms of the alkyl group are connected in
straight chain and there is no branching, it is called n-alkyl group.
H3C CH 2 CH2
H3C CH2 CH2 CH2
H3C CH2 CH2 CH2 CH2
n-propyl
n-butyl
n-pentyl or n-amyl
(N.B: Note that methyl and ethyl groups are named as such; not as n-methyl and n-ethyl,
because they do not have any other types like iso, sec- , tert- or neo)
Nomenclature
Compounds
of
Organic
H3C
(ii)
isoalkyl group: The group beginning with H C CH
3
unit and other carbon atoms if
any are connected in straight chain with no further branching is called isoalkyl group.
H3C
H3C
H3C
H3C
CH
(isopropyl),
H3C
CH CH 2
CH CH2 CH2
(isobutyl)
H3C
isopentyl or isoamyl
(iii)
secondary or sec-alkyl group:
When one H atom is removed from a secondary carbon atom, a sec- alkyl group results.
Butane gives sec-butyl and propane gives sec-propyl groups.
2
H3C
0
CH2 CH2
CH3
H3C
H3C CH2 CH
CH3
sec-butyl
CH3
CH2 CH
butane
In sec-alkyl group the unfulfilled valency of the alkyl group(shown by dash mark) is
connected to that carbon atom which is linking with one H atom.
20
H3C
H3C CH2
propane
H3 C
CH3
CH
CH
CH3
sec-propyl
H 3C
Note that sec-propyl group is same as isopropyl as it satisfies the requirements of both types.
Between the two names isopropyl is more popular and widely used. Note also that sec-alkyl
group is restricted to sec-butyl only because larger sec-alkyl groups do not have unique structure.
For example, sec-pentyl group can have two different structures which can be obtained from
pentane by removing one H atom from C-2 and C-3. But butane gives only one sec-butyl group
as C-2 position is unique.
(iv)
tertiary or tert-alkyl group:
When one H atom is removed from a tertiary carbon atom, a tertiarty or tert- alkyl
group results.
0
H3C
CH
CH3
H 3C
C
CH3
tert-butyl
CH3
CH3
CH3
CH3
3
0
H3C CH2
3
CH
H 3C CH2
C
CH3
tert-pentyl CH3
In tert-butyl group the unfulfilled valency of the alkyl group(shown by dash mark) is connected
to that carbon atom which does not link with any H atom. The use of tert-alkyl group is limited to
tert-butyl and tert-pentyl groups only as for higher tert-alkyl groups unique structures are not
possible.
(v)
neopentyl group: The alkyl group beginning with the following part structure(I) and
other carbon atoms if any are connected in straight chain is called neoalkyl group.
Concepts in
Chemistry
CH3
CH 3
H3C C CH2
(I)
H3 C
CH3
C CH2
(neopentyl)
H3 C
CH3
CH 3
(neohexyl)
C CH2 CH2
and
CH3
so on
Note that while iso and neo prefixes are integrated with the names of the alkyl groups, n-, secand tert- prefixes remain separated from alkyl groups by a hyphen.
SAQ IV.2: Draw the structures of the following alkyl groups
(i)n-hexyl
(ii)isohexyl
(iii)neoheptyl
NAMING OF COMPOUNDS USING COMMON OR TRIVIAL SYSTEMS:
1.
ALKANES:
(i)
normal or n-alkane: When the carbon atoms are connected in straight chain and
there is no branching, it is called a n-alkane. In other words one one H atom is attached with a nalkyl group it becomes a n-alkane.
H3C
CH2 CH2 CH3 (n-butane),
(ii)
isoalkane:
results.
H3C
CH CH2
(isobutane)
CH 3
(isopentane)
H3 C
When one H atom is attached with a neoalkyl group, a neoalkane
CH 3
CH 3
C
CH3 (n-pentane)
H3 C
CH CH3
H3 C
CH 2 CH2 CH2
When one H atom is attached with an isoalkyl group, an isoalkane
H3C
(iii)
neoalkane:
results.
H3C
CH3
(neopantane)
H3 C
CH 3
C
CH2
CH3
(neohexane)
CH 3
IMPORTANT: The names isobutane, isopentane and neopantane have been accepted as
sytstematic IUPAC names for those alkanes.
OLEFINES (ALKENES):
The first member of alkene is called ethylene and all other alkenes are expressed as
substituted ethylenes.
Monosubstituted ethylene:
If there is one alkyl substituent attached to any carbon atom of the C=C in place of one
H atom, then it is called alkylethylene. It is a monosubstitued alkene.
: H2C
CH2 ethylene(ethene);
H2C
CH
CH 3 propylene or methyl ethylene(propene)
Disubstituted ethylene
Disubstituted alkenes are classifed as (i)symmetrical or sym-alkene and (ii)unsymmetrical
or unsym-alkene.
Nomenclature
Compounds
of
Organic
Symmetrical alkene: If one H atom from each of the two doubly bonded carbon atoms is
substituted by same alkyl groups, it is a symmetrical alkene.
Unsymmetrical alkene: If two H atoms of any one doubly bonded carbon atom are substituted
by two same alkyl groups, it is an unsymmetrical alkene.
The IUPAC names have been given inside parentheses for comparison.
CH3 C CH2
CH3 CH CH CH3
CH3
sy m-dimethy lethy lene
(but-2-ene)
unsy m-dimethy lethy len
(2-methy lp rop ene)
Unsym-dimethylethylene(2-methylpropene) is also called isobutene or isobutylene.
ALKYNE:
The first member of alkyne is called acetylene and all other alkenes are expressed as substituted
acetylenes- (i)monosubstituted- if one H atom is replaced by an alkyl group or
(ii)disubstituted- if both the H atoms are replaced by alkyl groups
H3 C
HC
CH
acetylene
H3C C
CH
methylacetylene
H3C
C C CH3
dimethylacetylene
CH C CH
H3 C isopropylacetylene
SAQ IV.3: Draw the structures of the following compounds. Also give their IUPAC
names.
(i)isohexane (ii)neoheptane (iii)sec-butylethylene
(iv)sym-diisopropylethylene
(v)tert-butylacetylene
(vi)ethylisobutylacetylene
(vii)n-heptane
ALKYL HALIDE(HALOALKANE):
The haloalkanes are called alkyl halides in the common system. First the name of alkyl group
according to common system is written which is followed by the term halide(fluoride, chloride,
bromide, iodide) with a space in between.
CH3
H3C
CH
H3C
Cl
H3C
isopropyl chloride
(2-chloroprapane)
C
Br
H3C
CH2
CH2 I
CH3
n-propyl iodide
tert-butylbromide
(2-bromo-2-methylpropane) (1-iodopropane)
SAQ IV.4: Give the common names of the following alkyl halides, also write their IUPAC
names.
H3C
(i)CH3Br
(ii)CH3-CH2-Cl
(iii) (CH3)3C-I
(iv)
H3C
CH CH2 Br
SAQ IV.5: Draw the structures of the following and also give their IUPAC names.
(i)sec-butyl chloride (ii)neopentyl iodide
(iii)isohexylbromide (iv)tert-pentyl chloride
(v) n-propyl iodide
ALCOHOL:
In common system, an alcohol is named as alkyl alcohol. First the name of the alkyl group is
written according to common system, followed by the term alcohol with a space in between.
Concepts in
Chemistry
H3C
H3C CH2 CH OH
CH OH
H3C
isopropyl alcohol
(propan-2-ol)
CH3
sec-butyl alcohol
(butan-2-ol)
CH3
H3C C CH2 OH
CH3
neopentyl alcohol
(2,2-dimethylpropan-1-ol)
THIOALCOHOL:
In common system thioalcohol is named as alkyl mercaptan. First the name of the
alkyl group is written according to common system, followed by the term mercaptan with a
space in between.
H3C
3
SH
2
SH
H3C
CH3
H3C
1
sec-butyl mercaptan(butane-2-thiol)
isopropyl mercaptan (propane-2-thiol);
SALT OF ALCOHOL:
RONa or ROK are the salts of alcohol which are named as metal alkoxides. The
trivial name of the alkyl group is used to name the alkoxide.
H3C
O Na sodium isopropoxide(sodium propan-2-olate);
H3C
CH3CH2OK potassium ethoxide (potassium ethanolate)
SAQ IV.6: Give the names of the following according to common system.Also give their
IUPAC names.
(i) CH3-CH2-OH
(ii)CH3-OH
(iii) CH3-CH 2-CH 2-OH (iv)CH 3-CH(OH)-CH2CH 3 (v)(CH3)3COH
(vi)(CH3)2CHCH2CH 2OH
SAQ IV.7: Draw the structures of the following alcohols. Also give their IUPAC names,
(i) tert-pentyl alcohol (ii) n-butyl alcohol
(iii) isopropyl alcohol (iv)isobutyl
mercaptan
(v) sodium tert-butoxide
(vi)potassium methoxide
KETONES:
Ketone is named as alkyl alkyl ketone or dialkyl ketone having a space between any
two words.The two alkyl groups attached to the carbonyl group are written first in alphabetical
order followed by the term ketone. If the two alkyl groups are same then we write dialkyl
ketone. Note that the carbonyl carbon is excluded while naming the two alkyl groups and the
term ketone in the name signifies the carbonyl carbon atom.
O
CH3
C
CH3
dimethyl ketone or acetone (propanone)
The carbonyl(C=O) group is connected to two methyl(CH3)groups, hence the name dimethyl
ketone. ACETONE is its most popular name and has been accepted by IUPAC as official
name.
Nomenclature
Compounds
of
Organic
O
O
H3C
CH2 C
CH3
H3C CH2 CH
C
CH3
H3C
CH3
C
C CH3
C
CH3
CH3
ditert-butyl ketone
(2,2,4,4-tetramethylpentan-3-one)
CH3
sec-butyl methyl ketone
(3-methylpentan-2-one)
ethyl methyl ketone
(butan-2-one)
CH3 O
SAQ IV.8: Draw the structures and give IUPAC names of the following compounds.
(i) ethyl isobutyl ketone (ii)isopentyl n-propyl ketone
(iii)disec-butyl ketone
ALDEHYDE: Aldehydes have typical common names. Try to remember them.
O
O
H3C C H
H C H
formaldehy de acetaldehy de
(methanal)
(ethanal)
O
O
H3C H2C C H
p rop ionaldehy de
(p rop anal)
H3C
CH2
H2C C
buty raldehy de
(butanal)
H
The common names of the first four aldehydes are so widely popular that they are also regarded
as official names by IUPAC.
SAQ IV.9: Write the structure and IUPAC name of isobutyraldehyde
CARBOXYLIC ACIDS(FATTY ACIDS)
Carboxylic acids have similar names as aldehydes. They were called fatty acids because they
were first derived from natural fats.
O
O
H C OH
formic acid
(methnoic acid)
H3C C OH
acetic acid
(ethanoic acid)
O
O
H3C H2C C OH
propionic acid
(propanoic acid)
H3C
CH2
H2C C
n-butyric acid
(butanoic acid)
OH
The first four common names are also regarded as official names by IUPAC.
The common names of straight chain carboxylic acids containing greater number of carbon
atoms are given below.
C5- valeric acid(pentanoic acid) , C6-caproic acid(hexanoic acid), C8-caprylic acid(octanoic acid),
C10- capric acid(decanoic acid), C12-lauric acid(dodecanoic acid), C14-myristic acid(tetradecanoic
acid), C16-palmitic acid(hexadecanoic acid), C18-stearic acid(octadecanoic acid), C20-arachidic
acid(eicosanoic acid), C22-behenic acid(docosanoic acid), C24-lignoceric acid(tetracosanoic acid),
C26-cerotic acid(hexacosanoic acid), C30-melissic acid(tricontanoic acid), C7-oenanthylic
acid(hepatanoic acid), C9-pelargonic acid(nonanoic acid).
(NB: The students are advised not to remember these names. These are given only for
referenece)
CH3
H3C
2
COOH
COOH
1
3
CH3
pivalic acid
O
H 3C
(pyruvic acid)
COOH
H2C
acrylic acid
Concepts in
Chemistry
Pivalic acid(2,2-dimethylpropanoic acid) and acrylic acid(prop-2-enoic acid) are accepted also
as the IUPAC names. Pyruvic acid is named as 2-oxopropanoic acid by IUPAC system.
SAQ IV.10: Write the structures of the following and also give their IUPAC names.
(i)isobutyric acid
(ii)valeric acid (iii) isovaleric acid
(iv)palmitic acid
ESTERS:
-ate is used in place of -ic as suffix with the common name of the acid . Look
at the examples.
O
H3 C
C
O
CH 3
methyl acetate(methyl ethanoate). Here, the name of the acid in
common system is acetic acid hence the ester is named as acetate. Similary, other esters have
the parent name as formate, propionate, butyrate, valerate etc. The names formate, acetate,
propionate and butyrate are also regarded as official IUPAC names. In fact, the first four common
names of all the derivatives of carboxylic acids are regarded as alternative official names by
IUPAC.
O
H C
O
O
CH 3
H3 C CH 2 C
O CH
H3 C CH 2 CH 2 C O CH 2 CH 2 CH 3
O CH CH 2 CH 3
CH 3
CH 3
isopropyl formate
(isopropyl methanoate)
n-propyl butyrate
(n-propyl butanoate)
sec-butyl propionate
(sec-butyl propanoate)
SAQ IV.11: Draw the structures of the following and also give their IUPAC names.
(i)isobutyl acetate (ii)tert-butyl valerate
(iii)neopentyl laurate
(iv)sec-butyl
isobutyrate (v)n-amyl formate
ACID AMIDES:
-amide is used as suffix with the common name of the acid.
O
O
H
C
formamide (methanamide),
NH2
CH3 C
NH 2 acetamide(ethanamide)
Higher amides are propionamide(C3), butyramide(C5), valeramide(C5) and so on.
ACID CHLORIDE: -yl chloride is used in place of -ic chloride as suffix with the common
name.
O
CH3 C
Cl
acetyl chloride(ethanoyl chloride). Similarly, for higher members the
names are propionyl chloride, butyryl chloride, valeryl chloride and so on.
SALTS OF CARBOXYLIC ACID: -ate is used as suffix in place of -ic with the common
name of acid.
O
- +
H3C
C O Na
sodium acetate
(sodium ethanoate)
O
O - +
- 2+
Ca
H
C
C
O
3
H C OK
2
potassium formate
calcium acetate
(potassium methanoate) (calcium ethanoate)
Nomenclature
Compounds
of
Organic
ACID ANHYDRIDE: Anhydride is used as the suffix with the common name.
O
O
H3C C O
O
C
acetic anhydride(ethanoic anhydride) - symmetrical anhydride
CH 3
O
O
H3 C
C O C CH 2 CH3
acetic propinoic anhydride
(ethanoic propanoic anyhydride)
O
H3 C CH2 CH 2 C O C CH2 CH 3
unsym. anhydride
butyric propionic anhydride
(butanoic propanoic anhydride)
ALKYL CYANIDE(ALKANENITRILE): Name of the alkyl group in common system is
written first which is followed by the suffix cyanide with a space in between. Note that cyanide
carbon is not included while naming the alkyl group. In IUPAC naming the cyanide carbon is
included in the name(alkanenitrile).
CH3
CN
methyl cyanide
CH3 CH2 CN
ethyl cyanide
H3 C CH2 CH2 CN
n-propyl cyanide
(acetonitrile)
(propiononitrile)
(butyronitrile)
(propanenit rile)
(et hanenitrile)
(butanenit rile)
SAQ IV.12: Give the structures and IUPAC names in case of the following.
(i)isopropyl cyanide (ii)tert-butyl cyanide
(iii)potassium isobutyrate
(iv)butyric anhydride
α, β, γγ....system of naming :
In case of aldehyde, carboxylic acid and its derivatives this system of naming is followed. The
carbon atom adacent to the functional group is called alpha(α) carbon, the subsequent atoms are
called beta(β), gamma(γ), delta(δ). The substituents attached to those carbon atoms are written
first with the prefix α, β, γ... which are followed by the name of the parent compound in the
common system.
Br
CH3
CH2
CH




C
C
C
C
COOH
CH3 OH
COOH
H3C C
CH
O
C
H
CH3
β-bromo-α-methylpropionic acid
α-hydroxy-β,β-dimethylbutyraldehyde
SAQ.IV.13: Give the structures and IUPAC names of the following.
(i)β-amino-α-methyl propionamide (ii)isoproyl α-chloro acetate
(iii)β,β-dimethyl
butyryl chloride
(iv)γ-bromo-α,β-dimethylvaleric acid
AMINES:
1.
10 amine: Primary amine is named as alkyl amine. The common name of the alkyl
group is written first followed by the term amine.
Concepts in
Chemistry
CH3
H3C
H3C CH2 CH NH2
CH NH2
H3C
isopropyl amine
(propan-2-amine)
H3C
C
CH2 NH2
CH3
neopentyl amine
(2,2-dimethylpropan-1-amine)
CH3
sec-butyl amine
(butan-2-amine)
2.
20 amines: Sec-amines are named as alkyl alkyl amine when two alkyl groups are
different and dialkyl amine when the two alkyl groups are identical. Note that the common
names of alkyl groups are used.
CH3
H3C
H3C
CH NH CH2 CH3
H3C
ethyl isopropyl amine
(N-ethylpropan-2-amine)
CH CH2 NH CH2 CH
H3C
CH3
diisobutyl amine
(N-isobutyl-2-methylpropan-1-amine)
3.
30 amines: Tert-amines are named as alkyl alkyl alkyl amine when the three alkyl
groups are different and dialkyl alkyl amine when two alkyl groups are identical and the third
is different and trialkyl amine when the three alkyl groups are identical.
CH3
H3C CH2 CH N
CH3
H3C
CH2
CH3
H3C
CH
CH N CH3
CH3
CH2
H3C CH2 N CH2 CH3
H3C
CH3
triethyl amine
sec-butyl ethyl methyl amine
diisopropyl methyl amine
(N-ethyl-N-methylbutan-2-amine) (N-isopropyl-N-methylpropan-2-amine) (N,N-diethylethanamine)
ETHERS:
Ethers are named as alkyl alkyl ether or dialkyl ether depending on whether the alkyl groups
are respectively different or same. The common names of alkyl groups are used.
H3 C
CH O CH2 CH3
H3 C ethyl isopropyl ether
(2-ethoxypropane)
H3 C CH2 CH2 O CH2 CH2 CH3
di n-propyl ether
(1-propoxypropane)
CH3
O
H3C
CH3
CH3
H3C
sec-butyl tert-butyl ether
(2-tert-butoxybutane)
Nomenclature
of
Organic
Compounds
IMPORNTANT: The common names of ethers involving simple common alkyl groups like isopropyl,
sec-butyl, isobutyl, tert-butyl, neopentyl etc. as discussed above are sometimes used as the
preferred official names by IUPAC.
SAQ IV.14: Give the structures and IUPAC names of the following.
(i)tert-butyl amine
(ii)tert-pentyl n-propyl amine
(iii)trisec-butyl amine
(iv)ethyl diisopropyl amine(v)methyl neopentyl ether
(v)disec-butyl ether
PRACTICE QUESTIONS
1.
Write the structures of the following compounds. Also give their IUPAC names.
(i) n-butyl chloride
(ii)sec. butyl alcohol
(iii)Isopentane
(iv)n-hexane
(v)tert. butyl bromide (vi)n-pentyl alcohol
(vii)diethyl ketone
(viii)neohexane
(ix) neopentyl chloride (x)n-propyl formate
(xi)Isobutene (xii)dimethyl acetylene
(xiii)isopropylbutyrate (xiv)α-methyl-β-hydroxyvaleric acid
(xv)ethyl tert-pentyl ether
(xvi)isobutyl neopentyl amine
(xvii)triisopropyl amine (xviii)β-bromopivalic acid
(xix)calcium α-methylpropionate
(xx)α-methylbutyric anhydride
2. Give the structural formula and IUPAC names of the following.
(a)isobutyl chloride
(b)methyl neopentyl amine
(c)acetamide
(d)α-chlorobutyraldehyde
(e)tert-butyl ethyl ketone
(f)disec-butyl ether
(g)isopropyl alcohol
(h)N-secbutyl formamide
(i)isobutane
(j)tert-pentyl acetylene (k)β-methyl butyramide (l)isopentyl bromide
(m)diethyl isopropyl amine
(n)trimethyl amine
(o)isohexyl acetate
3.: Give the structure and IUPAC name of the following.
(a)vinyl chloride(b)allyl ethyl ether
(c)benzyl chloride
(d)n-hexyl alcohol
(e)cyclobutyl methyl amine
(f)but-2-enyl chloride (g)propargyl bromide
(h)ethylidene chloride (i)isopropylidene chloride
(j)ethylene dichlorde
(m)m-hydroxyphenyl isopropyl
(k)α-cyclohexyl acetaldehyde (l)allyl benzyl ether
amine
(n)1,1,3-trimethylbutyl n-butyl ether
(o)sodium laurate
4.
Write both common and IUPAC names of the following.
CH3
H3C
CH3
H3C
CH3
H3C
O
CH3
CH3
N
(i)
(ii)
H3C
CH3
(iii)
H3C
H3C
CH3
CH3
O
H3C
H3C
H3C
CH3
CH3
H3C
H3C
CH3
H
(iv)
(v)
CH3
O
CH3
CH3
Concepts in
Chemistry
H3C
H3C
OH
(vi)
Br
(vii)
H3C
H3C
CH3
CH3
RESPONSE TO SAQs
CH3
SAQ.IV.1:
(ii) H C
(i) CH4(methane)
CH3
3
(2,2-dimethylpropane)
CH3
H3C
CH CH2 CH2 CH2
(ii)
SAQ.IV.2: (i) CH3 CH2 CH2 CH2 CH2 CH2
H3C
CH3
(iii)
CH3 C CH2 CH2 CH2
CH3
CH3
3
H3C
1
CH3
2
4
5
3
2
H3C
1
SAQ.IV.3:
CH3
(i)
(ii)
2-methylpentane
CH3
2
(iii)
5
H3C
3
4
5
CH2
3
5
CH3
2,2-dimethylpentane
H 3C
H 3C
4
CH3
1
(iv)
2
4
H3C
CH3
1
6
2,5-dimethylhex-3-ene
3-methylpent-1-ene
CH3
2
H3C
3
2
CH
4
5
1
CH3
(vi)
CH3
CH3
6
H3C
1
4
(v)
3
7
6-methylhept-3-yne
3,3-dimethylbut-1-yne
(vii) CH3-(CH2)5-CH3 (heptane)
SAQ.IV.4: (i)methyl bromide(bromomethane)(ii)ethyl chloride(chloroethane) (iii)tertbutyl iodide(2-iodo-2-methylpropane) (iv)isobutyl bromide(1-bromo-2-methylpropane)
CH3
CH3
H3C
SAQ.IV.5:
(i)
Cl
2-chlorobutane
(ii)
CH3 C
CH2 I
CH3
(1-iodo-2,2-dimethylpropane)
Nomenclature
Compounds
of
Organic
CH3
4
2
2
H3C
Br
3
H3C
(iii)
CH3
3
4
1
Cl
H3C
(iv)
5
1-bromo-4-methylpentane
(v)
1
2-chloro-2-methylbutane
CH3 CH2 CH 2 I
1-iodopropane
SAQ.IV.6: (i)ethyl alcohol(ethanol) (ii)methyl alcohol(methanol)
(iii) n-propyl alcohol(propan-1-ol)
(iv)sec-butyl alcohol(butan-2-ol) ( v ) t e r t - b u t y l
alcohol (2-methylpropan-2-ol (vi)isopentyl alcohol(3-methylbutan-1-ol)
SAQ.IV.7:
CH3
3
OH
2
H 3C
4
OH
OH
H3C
H3C
(i)
(ii)
1
(iii)H3C
butan-1-ol
2-methylbutan-2-ol
H3C
CH3
propan-2-ol
CH3
H3C
(iv)
O Na
(v)
H3C
(vi)CH3OK
CH3
SH
2-methylpropane-1-thiol
sodium 2-methylpropan-2-olate
postassium methanolate
SAQ.IV.8:
H3C
O
8
CH3
3
H3C
1
2
(i)
5
4
H3C
CH3
5-methylhexan-3-one
CH3
(iii)
CH3
O
3,5-dimethylheptan-4-one
H3C
CHO
SAQ.IV.9:
4
1
2
O
7-methyloctan-4-one
CH3
H3C
(ii)
6
CH3
3
5
7
6
H3C
2-methylpropanal
Concepts in
Chemistry
SAQ.IV.10:
H 3C
H3C
COOH
3
H 3C
(i)
(ii)
COOH
H3C
(iii)
pentanoic acid
2-methylpropanoic acid
2
H3C
COOH
4
1
3-methylbutanoic acid
(iv)CH3-(CH2)14-COOH(hexadecanoic acid)
SAQ.IV.11:
O
H 3C
H3C
O
(i)H3C
3
H3C
CH3
O
(ii)
H3C
tert-butyl pentanoate
isopropyl acetate
(iii)
1
5
CH3
CH3
O
2
4
CH3
O
C CH2 O
C
(CH2 )10 CH3
(neopentyldodecanoate)
CH3
H 3C
CH 3
O
3
2
O
CH 3
1
O
(iv)
CH3
H
(v)
H 3C
O
pentyl formate
sec-butyl 2-methylpropanoate
(N.B: Note that acetate and formate are the IUPAC accepted names for ethanoate and methanoate
respectively)
SAQ.IV.12:
H 3C
CH3
3
2
(i)
H 3C
CN
1
H3 C
(ii)
2-methylpropanenitrile
CH3
2
3
CN
1
(2,2-dimethylpropanenitrile or pivalonitrile)
CH3
O
-
O
+
CH COOK
(iii) CH3
potassium 2-methylpropanoat
(iv)H3C
O
butanoic anhydride
CH3
Nomenclature
Compounds
of
Organic
SAQ.IV.13:
CH3
O
NH 2 CH3
Cl
O
C
NH2
(i) CH 2 CH
3-amino-2-methylpropanamide
CH3
O
(ii)
isopropyl chloroacetate
CH3
CH3
CH3
Br
H3C
Cl
CH3
(iii)
H3 C
(iv)
O
COOH
4-bromo-2,3-dimethylpentanoic acid
3,3-dimethylbutanoyl chloride
SAQ.IV.14:
CH3
2
H 3C
H 3C
4
NH2
(i)
2
3
(ii)
CH3
CH3
CH 3
H 3C
3
H3C CH2 CH N CH CH2
NH
(iii)
N,N-disec-buty lbutan-2-amine
1
2-methylpropan-2-amine
2-methyl-N-propylbutan-2-amine
CH 3
CH
(iv)
N
CH3
1
CH 2
H 3C
CH3
H3C CH CH2 CH3
CH 3
1
CH3
CH 3
H3C
CH
H 3C
2
O
3
(v)
CH 3
N -ethyl-N-isopropylpropan-2-am ine
CH3
CH3
1-methoxy-2,2-dimethylpropane
(vi)CH3CH2(CH3)OCH(CH3)CH2CH3 (2-sec-butoxybutane)
ANSWER TO PRACTICE QUESTIONS
1.
(i) H3C CH2 CH2 CH2 Cl (1-chlorobutane)
H3C
CH3
(ii)
H3C
CH2 CH OH
(butan-2-ol)
(iii)
H3C
CH CH2 CH3 (2-methylbutane)
CH 3
HC
(iv) H3C CH2 CH2 CH2 CH2 CH3 (hexane) (v) 3
C
Br
CH 3
(vi) H3C CH2 CH2 CH2 CH 2
OH (pentan-1-ol)
O
(vii)
H3C
CH2
C
CH 2
CH 3
(pentan-3-one)
(2-bromo-2-methylpropane)
Concepts in
Chemistry
CH 3
H3C
(viii)
C CH 2 CH 3
(2,2-dimethylbutane)
CH 3
CH3
H3C
(ix)
C CH2
Cl (1-chloro-2,2-dimethylpropane)
CH3
O
(x)
H
C O
CH 2 CH 2 CH 3
(propyl methanoate or propyl formate)
H3C
C
(xi)
CH 2
(2-methylpropene) (xii) H3C
H3C
H 3C
3
(xiii)
C
CH 3 (but-2-yne)
CH 3
O
2
4
C
1
(isopropyl butanoate or butyrate)
CH 3
O
CH3
OH
(xiv)H3C
OH
(3-hydroxy-2-methylpentanoic acid)
O
CH3
CH3
(xv)H3C
O
CH3
H 3C
NH
3
2
(xvi)
1
CH3
H 3C
(N-isobutyl-2,2-dimethylpropan-1-amine)
CH3
CH3
H3C
H3C
(xvii)
(2-ethoxy-2-methylbutane)
CH3
CH3
(N,N-diisopropylpropan-2-amine)
N
CH3
H3C
H3C
(xviii)Br
CH3
COOH
(3-bromo-2,2-dimethylpropanoic acid)
CH3
(xix) H C
3
CH
Ca (calcium 2-methylpropanoate)
COO
2
Nomenclature
Compounds
of
Organic
(xx) CH3CH2CH(CH3)COOCOCH(CH3)CH2CH3 (2-methylbutanoic anhydride)
(N,2,22. (a) (CH3)2CHCH2Cl(1-chloro-2-methylpropane) (b)MeNHCH2C(CH3)3
trimethylpropan-1-amine)
(c) CH3CONH2(ethananmide or acetamide)
(d)CH3CH2CH(Cl)CHO (2-chlorobutanal)
(e)(CH3)3CCOCH2CH3(2,2-dimethylpentan3-one) (f)[CH3CH2CH(CH3)]2O (2-sec-butoxybutane)
(g)(CH3)2CHOH(propan-2-ol) (h)HCONHCH(CH3)CH2CH3(N-sec-butylformamide or
methanamide)
(i) (CH3)3CH(2-methylpropane) (j) CH CC(CH3)(CH3)CH2CH3 (3,3-dimethylpent-1-yne)
(l)(CH3)2CHCH2CH2Br(1-bromo-3(k) CH3CH(CH3)CH2CONH2(3-methylbutanamide)
methylbutane)
(m) (CH3)2CHN(C2H5)(C2H5)(N,N-diethylpropan-2-amine)
(n)(CH3)3N(N,N-dimethylmethanamine)
(o) CH3COOCH2CH2CH2CH(CH3)2
3. (a) CH2=CHCl (chloroethene)
(c)C6H5CH2Cl(chloromethylbenzene)
NH
(e)
CH3
(b)CH2=CHCH2OCH2CH3(3-ethoxypropene)
(d)CH3(CH2)4CH2OH(hexan-1-ol)
(N-methylcyclobutanamine)
(f)CH3CH=CHCH2-Cl(1-chlorobut-2-ene)
Cl
(g) HC
H3C
(i)
H3C
C CH2 Cl (3-chloropropyne) (h) H3C CH
Cl
(1,1-dichloroethane
Cl
C
Cl
(2,2-dichloropropane)
(j) ClCH2-CH2Cl(1,2-dichloroethane
(k) (C6H11)CH2CHO (2-cyclohexylethanal)
(l) PhCH2OCH2CH=CH2([(allyloxy)methyl]benzene or 3-benzyloxypropene)
HO
CH3
(m)
[3-(isopropylamino)phenol]
CH3
NH
CH3
O
(n)H3C
(2-butoxy-2,4-dimethylpentane)
CH3
CH3
CH3
(o)CH3(CH2)10COONa (sodium dodecanoate)
4. (i)isoamyl tert-pentyl ether [1-(tert-pentoxy)-3-methylbutane or 1-(1,1-dimethylpropyl)-3methylbutane] (ii) sec-butyl tert-butyl ethyl amine[N-(tert-butyl)-N-ethylbutan-2-amine
(iii)isopropyl neopentyl ketone [2,5,5-trimethylhexan-3-one] (iv) α-isopropyl-βmethylbutyraldehyde[2-isopropyl-3-methylbutanal] (v)isobutyl tert-pentyl acetylene[2,6,6trimethyloct-4-yne] (vi) neohexyl alcohol[3,3-dimethylbutan-1-ol] (vii)neoheptyl bromide[1-bromo4,4-dimethylpentane]
Concepts in
Chemistry
PREFERRED IUPAC NAMES(PIN)
The 1993 recommendations of IUPAC have allowed the use of more than one names for a
single structure provided the different names can unambiguously represent the same structure.
Names based on older IUPAC rules and also names from tradional origin could be officially
used as general IUPAC names of a compound. However out of these names the one which is
based strictly on the latest IUPAC recommendations(2004) is called the PREFERRED IUPAC
NAME(PIN). Other names than the PIN if any can also be used as official names as long as
the names respresent the same structure without any ambiguity. This popular stand taken by
IUPAC is based on the principle that a single organic structure can have more than one IUPAC
names but a single name cannot represent more than one structure. A few examples will make
this point clear. Below you find a table giving the PIN and other IUPAC names of a few
compounds.
Name of the
compound
Preferred
IUPAC name(PIN)
Other
IUPAC name
acetone
propan-2-one
but-3-en-2-ol
3-buten-2-ol
but-1-ene
1-butene
1-ethoxypropane
ethyl propyl ether
3-methylbutan-2-one
isopropyl methyl
CH3COOH
CH3CN
NC-CH2-CH(CN)CH2CN
acetic acid
acetonitrile
propane-1,2,3-tricarbonitrile
HCHO
formaldehyde
glycerol
ethanoic acid
ethanenitrile
3-cyanopentane
dinitrile
methanal
propane-1,2,3-triol
O
H 3C
C
CH
3
OH
H 3C
CH
CH
H2C
CH CH2
H3C
H2
C
CH 2
CH3
H2
C
O
H2
C
CH 3
O
H 3C
CH
C
CH 3
H 3C
CH2(OH)CH(OH)CH2OH
ketone
In the chapters I, II and III of the organic nomenclature part of this book, the PINs are
highlighted for structures carrying more than one IUPAC names. One thing you bear in mind
that whatever be the name of a compound if that name can generate an unambiguous structure,
the name has to be accepted with due honour even if that may not be preferred IUPAC name.
Nomenclature
Compounds
of
Organic
MISCELLANEOUS PRACTICE QUESTIONS
Give the preferred IUPAC names(PIN) and other names if any for the following compounds.
1.
CH3-O-CH2-CH2-O-CH2-CH2-O-CH2-CH3
H2
C
O
O
C
H2
CH 3
CH 3
CHO
O
2.
3.
4.
CHO
S
HO
O
OH
O
5.
CH3
HO
C
6.
O
7.
H3C
O
O
CH 3
CH3
H3C
8.
9.
Cl
CH 3
O
CH3
10. H C
O
11.
12.
3
O
NH
13.
NH
CH3
H3C
NH
14.
O
15.
16.
Cl
OH
HC
Br
17.
O
CHO
Concepts in
Chemistry
4
OH
5
3
6
2
CH3
18.
O
O
O
CH3
19.
NH
20.
CH3
O
1
CH3
OH
21.
CH3
O
O
22.
O
CH3
CH3
CH3
23.
24.
H 3C
CH 3
25.
CH 3
H3C
CH3
CH3
OH
O
26.
27. H C
OH
3
H3C
CH3
CH3
O
28.
29.
O
H 3C
CH 3
CH3
30.
CH2
H2C
CH3
CH2
CH3
31.
32.
Nomenclature
Compounds
of
Organic
SH
O
N
6
CH3
5
O
33.
34.
O
OH
1
35. 4
2
3
CH3
CH3
O
OH
Br
CH3
1
H3C
Cl
2
S
36.
37.
5
3
Br
CH3
Br
4
COOH
HO
CH3
Br
38.
39.
CH3
NO2
HO
CH3
3
4
CH3
40. H2C
41.
NH
2
5
N
H
1
CH3
O
4
42.
5
3
6
2
O
H3C
CH 3
N
O
43.
1
CH3
CH3
CH3
44.
45.
CH3
O
CH3
Concepts in
Chemistry
Answers to Miscellaneous Practice Questions
1. 1-ethoxy-2-(2-methoxyethoxy)ethane (PIN)/2,5,8-trioxadecane
2. propyl 4-hydroxybenzoate
3. phthalaldehyde(PIN)/benzene-1,2-dicarbaldehyde
4. 4-methylbenzenesulfonic acid(PIN)/p-toluenesulfonic acid
5.4-isopropylcyclobut-2-en-1-ol(PIN)/ 4-isopropyl-2-cyclobuten-1-ol
6. cyclohexylidenemethanone 7. cyclohexane-1,3,5-trione
8. 1-tert-butyl-4-cyclopropylcyclohexane 9. 3-chloro-6-ethylbicyclo[3.2.0]heptane
10. (2E,4E)-hexa-2,4-diene (if the groups lie on the opposite sides, it is called E(trans) and the
groups lie on the same side it called Z(cis). In this case, at each C=C, the two groups connected
lie opposite to each other. More about E and Z, you will know in the chapter stereoisomerism not
given in this book)
11. 7-oxabicyclo[4.1.0]heptane(PIN)/1,2-epoxycyclohexane 12. 2-oxocyclohexanecarbaldehyde
13. N-methyl-N’-propylmethanediamine
14. N-phenylcyclohexanecarboxamide
15. 5-bromo-6-chlorocyclohex-1-en-3-yne
16.pent-4-yn-1-ol
17. dioxane(PIN)/1,4dioxacyclohexane
18. Furan-2,5-dione(PIN)/maleic anhydride
19. 3-(isopropylamino)-2-methylcyclohexanol
20.3,4-dihydro-2H-pyran(PIN)/oxacyclohex-2ene
21. 3-(methoxymethoxy)propanoic acid 22. (1R,2R)-1,2-dimethylcyclohexane(PIN)/
trans-1,2-dimethylcyclohexane ( when two substituents remain on opposite sides i.e away from
each other it is called trans isomer. 1R, 2R refer to configurational identity of the carbon atoms
which will not to be discussed here)
23. (1R,2S)-1,2-dimethylcyclobutane(PIN)/cis-1,2dimethylcyclobutane( when two substitutents remain on the same side i.e close to each other, it is called
cis isomer. 1R, 2S refers to configurational identitity of carbon atoms, not to be discussed here)
24. (2Z)-4-methylpent-2-ene(PIN)/cis-4-methylpent-2-ene (when branches lie on the same same
side of the C=C, it is called trans Z or cis isomer)
25. (2E)-pent-2-ene(PIN)/trans-pent-2ene(when branches like on the opposite side of the C=C, it is called E or trans isomer)
26. (2E)-3,7-dimethylocta-2,6-dien-1-ol ( 2E indicates that in the C=C at C-2, the senior alkyl
groups lie on the opposite side)
(Note that R,S notations belong to optical isomerism and E, Z notation belong to geometrical
isomerism. These two isomerism belong to stereoisomerism. You will know the details of
isomerism from other books. Here the basis of writing full correct name is given. The beginners
will definitely face difficulty in naming such stereoisomeric structures until they study the chapter
stereoisomerism. So you are advised not to bother about E/Z and R/S now until you study that)
27. 2-(pentyloxy)ethanol
28. 1-(prop-1-enyloxy)acetone
29. 1-(but-2-enyl)cyclohexene (note that in Q. 28 and 29, the stereochemical notation E has
been dropped)
30.isoprene(PIN)/2-methylbuta-1,3-diene
31. styrene(PIN)/vinylbenzene
32. 1,6-dimethylcyclohexene(not 2,3-dimethylcyclohexene as it violates the lowest set of locants
rule)
33. dimethyl phthalate
34. 2-ethylcyclobutanecarbonitrile
35. 6-mercaptocyclohex-4-ene-1,3-diol (lowest set of locants for -ol followed by lower locant to ene gives the correct name)
36. 3-(ethylthio)hexane
37. 1,3,5-tribromo-2-chlorobenzene
38. 2-bromo-5-hydroxy-3-nitrobenzoic acid
39. 2-(3-methylbutyl)cyclopentanol
40. N-methylhex-5-en-1-amine(PIN)/N-hex-5-enyl-Nmethylamine
41. 3-methylpyrrole
42. 2-methylpyridine
43. 2-[2-(ethoxymethoxy)ethoxy]butane 44. 1-ethyl-3-methoxybenzene
45. 1-but-1-enyl-4-methylbenzene/ 1-[(1Z)-but-1-enyl]-4-methylbenzene
Nomenclature
Compounds
of
Organic
REFERENCES
1.
Nomenclature of Organic Chemistry (1979 Edition)
J.Rigauidy and S.P.Klesney, Pergamon Press, OXFORD
2.
A guide to IUPAC nomenclature of Organic Compounds (1994 edtion)
R. Panico, W. H. Powell and Jean-Claude Richer,
Blackwell Scientific Publications, OXFORD
3.
IUPAC Recommendations(2002); www.iupac.org
4.
On-line IUPAC Naming : www.iupac.org/nomenclature
5.
Schaum’s 3000 Solved Problems in Chemistry,
D. E. Goldberg, McGraw Hill Book Companty(New York)
Concepts in
Chemistry
Chapter-IV
ISOMERISM
Organic compounds have a unique charateristics of exhibiting isomerism. We have mentioned
this in the chapter "chemical bond" under covalent bonding. Organic molecules contain covalent
bonds between the various atoms and can be arranged in various different ways to give different
compounds having same formula. Isomers are different compounds having different
properties but having same chemical formula. The phenomenon is called isomerism. There
are two types of isomerism namey structural isomerism and stereoisomerism. We shall only
discuss structural isomerism now and in higher classes we shall study stereoisomerism. In
structural isomerism, the structures of the isomers are different. Look to the following example.
Molecular Formula:
C 4 H 10
This is an alkane, as it is in agreement with the formula CnH2n+2 where n=4. We can have two
alkanes possible from this formula.
H3C
H3C CH2 CH2 CH3 (butane)
H3C
CH CH3
(2-methylpropane or isobutane)
The two compounds have the same formula(C4H10), but their structures are different, their
names are different. Their properties are different for example, their boiling points are different.
These are called structural isomers. Commonly when we say isomerism, we mean the structural
isomerism. Let us study more about structural isomerism in a systematic way.
1.
Isomerism in Alkanes:
(i)The formula CH4, C2H6 and C3H8 have no isomers. But from C4H10 onwards,
isomerism is exhibited. We have already discussed isomerism in C4H10.
(ii)Isomerism in C5H12: Try to write as many structures as possible from the formula
C5H12. Name each by IUPAC system.
H3 C CH2 CH2 CH 2 CH3
H3 C
CH
(pentane or n-pentane)
CH2 CH 3
(2-methylbutane or isopentane)
CH 3
CH 3
H3 C
C
CH3
(2,2-dimethylpropane or neopentane)
CH 3
Try for more. You will not find any other isomer than the above three. You can know this when
you wirte the IUPAC name of a suspected new isomer. It will be merely repetition of the
previous isomers. Thus the formula C5H12 can have three isomers.
2.
Isomerism in Alkenes(CnH2n)
The formula C2H4, C3H6 do not exhibit isomerism. Isomerism starts from the formula
C 4H8.
Nomenclature
Compounds
of
Organic
Isomerism in C4H8: There are three isomers possible from this formula.
H2 C
CH
CH 3 (but-1-ene), H3 C
CH 2
CH
CH 3 (but-2-ene)
CH
H3 C
C
H3 C
CH2 (2-methylpropene or isobutene)
Can you get any other structural isomer from this formula? Try. You will not find any more.
3.
Isomerism in Alkyne(CnH2n-2 ):
C2H2, C3H4 do not show isomerism. However from C4H6 onwards, we find more than
one isomers from each formula.
Isomerism in C4H6: You know that alkynes contain one triple bond. Only two isomers
are possible.
HC
yne)
4.
C
CH3 (but-1-yne)
CH2
H3C
C
C
CH3 ( b u t - 2 -
Isomerism in Haloalkanes:
Mono haloalkanes(haloalkane containing one halogen atom) containing more than three
carbon atoms show isomerism. Look to this example.
Formula: C3H7Cl: We have two isomers possible from this formula.
H3 C
CH2
CH2
Cl (1-chloropropane)
Cl
H3 C
CH
CH3
(2-chloropropane)
Isomerism in Alcohols/Ethers(CnH2n+2O)
The formula for both alcohol and ether is CnH2n+2O. See this example.
(i)
Isomerism in C2H6O:
We can get only one alcohol from this formula i.e CH3-CH2-OH(ethyl alcohol). We can
get one ether from the same formula i.e CH3-O-CH3(methoxy methane or dimethyl
ether).
So alcohol and ethers are isomers.
(ii)
Isomerism from the formula C3H8O:
Alchohols: We can have two alcohols from this formula.
5.
H3C
CH2 CH2 OH (propan-1-ol or n-propyl alchohol)
OH
H3C
CH
CH3
( propan-2-ol or isopropyl alcohol)
Ethers: We can have only one ether possible from this formula.
H3C
CH2 O
CH 3 (methoxyethane or ethyl methyl ether)
Concepts in
Chemistry
6.
Isomerism in Aldehydes/Ketones(CnH2nO):
The formula for both aldehyde and ketone is CnH2nO. These are isomers. See this
example.
(i)
Isomerism in C3H6O: We can get one aldehyde and one ketone from this fomula.
O
O
H3C
(propanal)
H
CH 2 C
H3C
C
CH 3
(propanone
or
acetone)
(ii)
Isomerism from the formula C4H8O:
Aldehydes: Two aldehdydes are possible from the formula.
O
H3C
CH 2 CH2
C
H
(butanal),
CH 3 O
H3C
CH
C
H
(2-methylpropanal)
Ketone: Only one ketone is possible from this formula.
O
H3C
C
CH2
CH3
(butan-2-one or ethyl methyl ketone)
Are you thinking of another ketone , butan-3-one(!!!). There is nothing called butan-3one. This name is wrong. The locant of -one(ketone) should be minmum. Reverse the
numbering and you will find it to be butan-2-one.
7.
Isomerism in Carboxylic Acids and Esters(CnH2nO2 ):
Carboxylic acids and esters have the same formula CnH2nO2 and they are isomers.
(i)
Isomers from the formula C3H6O2:
Carboxylic acid: Only one carboxylic acid is possible.
O
H3 C
CH2
C
OH
(propanoic acid).
Esters: Two esters are possible from this formula.
O
H3 C
C
O
CH3 (methyl ethanoate or methyl acetate)
O
H
C
O
CH 2
CH 3
(ethyl methanoate or ethyl formate)
Thus we found here that the formula C3H6O2 gave rise to three isomers, one among them is a
carboxylic acid and the other two are esters.
Nomenclature
Compounds
of
Organic
SAQ 1: Write down the structures and names(IUPAC) of all the isomers possible from the the
following formula.
(1)C 6H 14
(2)C 4H 10 O
(3)C5H 8
CLASSIFICATION OF STRUCTURAL ISOMERISM:
There are many types of structural isomerism out of which we have already discussed
the following three types.
(a) Chain Isomerism: The isomers differ in the nature of carbon skeleton(word
root). Examples:
(i)Butane and 2-methylpropane
(ii) pentane and neopentane etc.
(b) Position Isomerism: The isomers differ in the position of functional group
or braches while the carbon skeleton remaining the same. The word root remain the same.
Examples:
(i) But-1-ene and but-2-ene
(ii) propan-1-ol and propan-2-ol
(iii) pentan-2-one and pentan-3-one
(c) Functional Isomerism: The isomers differ in the nature of the functional
groups.
Examples:
(i) Ethanol and methoxymethane (alcohol and ether)
(ii) propanone and propanal (aldehyde and ketone)
(iii) ethanoic acid and methyl methanoate (carboxylic acid and ester)
Other structural isomerisms such as tautomerism, metamerism and ring-chain isomerism have
not been discussed here.
RESPONSE TO SAQ
SAQ 1:
H3C
H3C
CH2 CH2
CH
CH 2
CH 2 CH2
CH2
CH2
(hexane or n-hexane)
CH3
( 2-methylpentane or isohexane)
CH 3
H3C
CH3
CH
CH 2
CH 3
(3-methylpentane)
CH 3
CH3
H3C
C
CH3
CH2
CH3
(2,2-dimethylbutane or neohexane)
Concepts in
Chemistry
CH3 CH 3
H3C
CH
CH
CH 3
(2,3 dimethylbutane
2.
The formula C4H10O is in agreement with the general formula, CnH2n+2O. This belongs
to the category alcohol/ether.
Alcohol: Four alcohols are possible from this formula. You can try for more, but you
shall fail.
(i) H3C CH2 CH2 CH2 OH (butan-1-ol or n-butyl alcohol)
OH
(ii) H C CH CH CH (butan-2-ol or sec. butyl alcohol)
3
2
3
CH3
(iii) H C CH CH OH (2-methylpropan-1-ol or isobutyl alcohol)
3
2
OH
(iv)
H3C C CH3
( 2-methylpropan-2-ol or tert. butyl alcohol)
CH3
Ether: There are three ethers possilbe from the formula.
(i) H3C CH2 O CH2 CH3 (ethoxyethane or diethyl ether)
(ii) H3C O CH2 CH2 CH3 (1-methoxypropane or methyl n-propyl ether)
CH3
(iii) H3C O CH
3.
CH3
(2-methoxypropane or methyl isopropyl ether)
C5H8 agrees to the formula CnH2n-2. It is an alkyne. Three isomers are possible.
(i) HC
C CH2 CH2 CH3 (pent-1-yne)
(ii) CH3
C
C CH2 CH3 (pent-2-
yne)
CH3
(iii) HC
C
CH
CH3
(3-methylbut-1-yne)
Other isomers containing two double bonds are also possible which we shall not take
now.