Unit M: Organic Chemistry
Heath-Chap 23, Hebden-Unit X p.213
I -Introduction
Def: Chemistry of carbon compounds
Some compounds are produced synthetically, some occur naturally, some are beneficial, some
are hazardous.
Where are they found?
Petroleum, natural gas, all living things (trees, grasses, vegetables, insects, animals, people
Manufacture of petrochemicals-largest industry involving organic chemistry
Petroleum is separated (fractionated) and refined for use in gasoline, oil and production of
plastics, solvents, pharmaceuticals and personal care products.
Ex: food additives, junk food ingredients
Hydrocarbons: compounds containing only carbon and hydrogen atoms.
II- Alkanes
Carbon atom can form bonds to 4 other atoms
Carbon has a valence of 4, tetravalent
When 1 or more of the 4 bonds connect to other carbon atoms, each of these attached
carbons can connect to 3 other atoms
Re: Hebden p.214
A. Straight Chain Alkanes (Unbranched)
3 ways to represent hydrocarbon formula:
Molecular formula
Full structure
Condensed structure
ex: propane molecule Heb p.215
Molecule differs by number of carbon atoms linked to one another to form a carbon chain.
Chain of carbon atoms extends in straight-line:
Straight-chain
Unbranched hydrocarbons
re Heath Table 23-1 p. 676, Heb p. 215
Alkane: hydrocarbon where all carbon atoms are connected by single bonds
Naming: alkanes compounds end in ”ane”
ex: methane, propane, butane…
.Saturated: each carbon bonded to maximum number of other atoms; carbon’s ability to
bond to other atoms is “saturated”.
Exercise:
1-Look at the sequence of hydrogen atoms connected to carbon atoms in the list below:
1
CH4, C2H6, C3H8, C4H10, C5H12
Suggest a general formula for all straight-chain alkanes. If there are “n” carbons, how many
hydrogens will be present? CnH?
B. Alkyl Groups and Branched Hydrocarbons
Hydrocarbon chain has “side branches” called alkyl groups
CH3-CH2-CH-CH2-CH2-CH3
I
CH2
I
CH3
Organic Compound Naming
Organic chemistry is like another language with specific rules
Organic language: basic words are placed together to make complete names for organic
molecules.
Organic words can have their endings modified and used like adjectives, verbs or adverbs
Always be sure to know the “syntax” or set of rules for constructing organic “sentences” that
make up the complete organic names of molecules.
Alkyl group: alkane which has lost one hydrogen atom
Unused bond can be connected to another hydrocarbon chain
Naming Rule: changing the “ane” ending to “yl”
Alkane Molecule
Alkyl Group
methane = CH4
methyl = CH3ethane = CH3-CH3
ethyl = CH3-CH2propane = CH3-CH2-CH2
propyl = CH3-CH2-CH2butane = CH3-CH2-CH2-CH3
butyl = CH3-CH2-CH2-CH2When alkyl group is attached to another hydrocarbon, resulting molecule
Is called a branched hydrocarbon or a substituted hydrocarbon
Rule: first step in naming a branched hydrocarbon is to find the longest continuous chain of
carbon atoms. Longest chain: parent hydrocarbon
To find longest chain: look at every “branch point” carbon and decide which two branches
create the longest overall path. (Only carbons are shown to make various branches easier to
see
a) C – C – C – C – C – C
I
C–C–C
b) C – C C –C
I I
Longest path (bold): 7 carbons; heptane
No “unique” path” exists.
Longest path: 6 carbons; hexane
2
C–C–C–C
I I
C – C C –C
c) C – C – C – C
C–C–C
I
I
C–C–C–C–C–C
I
C–C
Longest path: 9 carbons; nonane
Exercise Heb p. 218 #2
Alkyl Hydrocarbon Naming:
Name longest (parent) hydrocarbon chain and name various alkyl groups attached to parent
hydrocarbon.
Rule: Carbon atoms in parent chain are numbered consecutively from the end of the hydrocarbon
that gives the lowest possible set of numbers to the attached groups
Example:
1
2
3
4
5
CH3 – CH – CH2 – CH2 – CH3
2-methylpentane
I
CH3
Naming Rules:
1-carbon number at which alkyl group is attached
2-a dash
3-name of alkyl group
4-name of longest hydrocarbon chain to which the alkyl is attached
Examples:
8
7
6
5
4
3 2
1
CH3 – CH2 – CH2 – CH2 – CH2 – CH – CH2 - CH3
I
CH3
1
2
3
4
5
6
7
8
CH3 – CH2 – CH2 – CH – CH2 – CH2 – CH2 - CH3
I
CH2 – CH3
3 4
5
6
7
CH3 – CH – CH2 – CH2 – CH2 – CH3
I
CH2 – CH3
1
2
3-methyloctane
4-ethyloctane
3-methylheptane
3
Exercise Heb p. 219 #3
Heath p. 679 1-5
Tetravalent Carbon Atom
Bond With Carbon Atom(s)
Carbon attached to one C atom
Carbon attached to two C atoms
three C atoms
Becomes
CH3 - CH3
CH3 - CH2 - CH3 Carbon attached to
CH3 - CH - CH3
I
CH3
CH3
Carbon attached to four C atoms
I
CH3 - C - CH3
I
CH3
Exercise Heb p. 220 #4-6
Rule:
If there are more than one different alkyl group attached to a hydrocarbon;
.list the alkyl groups alphabetically
.precede each alkyl group by its number
.put a dash between each alkyl group and its number
Examples Heb p. 220
4-ethyl-2-methyloctane
3-ethyl-3-methyloctane
(2 groups can be attached to same carbon)
5-ethyl-3-methyl-6-propyldecane (tricky!!)
Rule:
If an alkyl group is repeated, then
.list each carbon number where the repeated group is attached,
separated by
commas
.prefix the repeated group name by di, tri, tetra, etc, to show how many identical
groups are attached.
Examples Heb p. 221
2,4,6-trimethylloctane
4,4-diethyl-2,2,7-trimethyl-7-propyldecane
Exercises Heb p.221 #7-9
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Structural Isomers
Compounds which have the same molecular formula but a different arrangement of atoms.
Example” C4H10 can refer to either:
CH3 - CH2 - CH2 –CH3
or
CH3 - CH - CH3
I
CH3
Each structural isomer has chemical/physical properties different from other isomers with the
same chemical formula
Exercises Heb p.222 #10-13
Alkanes Properties:
Unreactive since C – C and C – H bonds: strong, difficult to break
.methane, ethane, propane, butane: gases at room temperature
.pentane and longer chains: liquids
.very long chains(C116H34): solids, waxes or paraffins
C. Cycloalkanes
Cyclic hydrocarbons: chains where head connect to tail
Examples: cyclopropane
C3H6
cyclobutane cyclopentane cyclohexane
C4H8
C5H10
C6H12
Exercises Heb p.222 #14
Substituted Cycloalkanes
Rule:
.same rule as sraight-chain alkanes except:
.single substituent doesn’t use a number since all carbons in the cycloalkiyl are identical
.more than one substituent, the first substituent is given the “1” position and remaining
substituents are numbered to have the lowest set of overall values.
Examples:
methylcyclohexane
1-ethyl-2-methylcyclohexane
1,1-dimethylcyclopentane
Exercises Heb p.223 #15-16
5
III-Alkyl Halides
Alkane compounds with halogen substituents (F, Cl, Br or I)
Alkyl Halides Naming:
.same manner as alkyl groups
.attached F, Cl Br or I atoms called: fluoro, chloro, bromo and iodo groups
.use number to indicate attachment position on hydrocarbon chain
.if more than one of same kind of halogen is present, use prefixes di, tri, etc.
.if compound contains both alkyl and halo groups, list attached groups in alphabetical
order. Start numbering from the end which gives the lowest set of numbers.
Examples:
Chloromethane
2-fluoropropane
1,1,1-trichloro-2,2,2-trifluoroethane
3-bromo-1,6diiodononane
2,2-dibromo-3-methylhexane
fluorocyclopentane
Alkyl Halides Properties:
Insoluble in water (like alkanes)
.compounds with fluorine atoms: unreactive (inert) ex: Teflon
.chloro, bromo compounds can be reactive under drastic conditions
.iodo compounds: more reactive
Exercises Heb p.225 #17-20
IV-Multiple Bonds (Alkenes and Alkynes)
Alkene: compound containing a C – C double bond
Alkyne: compound containing a C – C triple bond
Example ethane, ethyne
Multiple Bonds Naming
If a double bond is present, change the “ane” ending to “ene”
If a triple bond is present, change the “ane” ending to “yne”
The bond number goes from the lower numbered carbon to the higher numbered one. The
number goes immediately in front of the name of the parent hydrocarbon, separated by a
hyphen.
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Number the compound to give the double/triple bond the lowest possible number. If the
number is the same starting from either end, start the numbering from the end closest to the
first branch point (where a group is attached).
Easy way to remember bond endings:
Use alphabetical order:
Single bonds Double bonds
Triple Bonds
Ane
Ene
Yne
Alkenes and alkynes: unsaturated hydrocarbons, since they have less hydrogen atoms than
equivalent alkanes.
Alkanes: saturated, since they contain maximum number of hydrogen
Writing Condensed Structure of Alkenes and Alkynes
1-Write the condensed formula
2-Write all the carbons in a row with spacing in between them
3-Number each carbon atom
4-Insert the specific bonds
5-Write the correct number of hydrogen for each carbon, knowing that carbon is tetravalent.
Examples: Heb p.227
2-hexene
ethane or ethylene
2-butene
3,3-dimethyl-1-pentene
propyne
4-methyl-1-pentyne
1-pentyne
propene
2-methyl-1-butene
ethyne or acetylene
2-butyne
3,3-dime3thyl-1-cyclopentyne
Exercises Heb p.228 #21-25
Geometry of Alkenes and Alkynes
Molecular representations: ethylene and acetylene
Alkenes: 3 atoms connected to each carbon lie flat, arranged 120° from each other
Alkynes: 2 atoms attached to central carbon lie in straight line, 180° from each other
Alkenes have rigid structure forming another kind of isomerism
Cis-Trans Isomerism requires
Double bond
Groups other than hydrogen attached to each carbons
Example: 2-pentene forms cis-2-pentene and trans-2-pentene
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Cis isomer: 2 groups are on the Same Side of double bond
Trans isomer: 2 groups are Transverse(opposite sides of double bond) to each other
Exercises Heb p.230 #26-28
V- Aromatic Compounds
Benzene C6H6 has the following structure
Ring-like structure has 2 resonance structures, consisting of alternating single and double
bonds between carbon atoms
Actual arrangement of electrons in carbon ring is a mixture of both resonance structures.
Benzene is represented as follow
Benzene’s resonance structures gives it unusual stability, highly resistant to chemical reaction.
Atoms attached to benzene ring can be replaced
Aromatic molecule: contain one or more benzene rings.
Compounds are fragrant and have pleasant scents
Aromatic Naming:
Identical to naming procedure used for cyclic hydrocarbons.
Examples:
Hydroxybenzene or phenol methylbenzene or toluene
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1,4-dichlorobenzene or paradichlorobenzene
Exercises Heb p.232 #29-31
VI- Functional Groups
Specific group of atoms that gives a molecule an ability to react in a specific manner or gives it
special properties
By adding functional groups to hydrocarbons a chemist can:
.make molecule act as acid, base or both
.give molecule a particular solubility
.give molecule a pleasant or unpleasant smell
.make molecule react with specific chemicals
.make molecule explosive
A. Alcohols
Compound containing OH group
Naming Rule
.number hydrocarbon chain to give the lowest possible number to OH group
.place number immediately before the name of parent hydrocarbon, separated by a dash. Alkyl
groups and their numbers are placed in front of the number for the OH
.indicate the presence of an OH group by changing the “e” ending of the hydrocarbon chain to
“ol”. (ending “ol” comes from alcohol”)
Examples:
CH3 – OH
methanol or methyl hydrate
CH3 – CH2 – OH
ethanol (drinking alcohol)
CH3 – CH – CH2 – CH3
2-butanol
I
OH
CH3 – CH – CH2 – CH – CH2 – CH3
5-methyl-3-hexanol
I
I
CH3
OH
Alcohol Properties:
2 opposing properties:
OH group: soluble in water, due to hydrogen bond
Non-polar hydrocarbon chain: insoluble in water
Methanol, ethanol, propanol: water soluble since hydrocarbon chain is small
Butanol: moderately soluble
Pentanol and higher alcohols: insoluble since long hydrocarbon chain
All alcohols are poisonous, ethanol is less poisonous
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Exercises Heb p.234 #32-33
B. Other Functional Groups
Not required to know how to name these functional groups
Aldehydes
Organic compound containing a C = O group at the end of a hydrocarbon chain
O
II
Aldehyde group:
-C-H
Examples:
O
II
H–C-H
CH3 – CHO
CH3 – CH2 – CH2 – CH – CHO
I
CH3
formaldehyde (common name), methanal
ethanal
2-methylpentanal
benzaldehyde
Ketones
Organic compound containing a C = O group at a position other than at the end of a
hydrocarbon chain.
Examples:
O
II
CH3 – C - CH3 or CH3COCH3
CH3CH2COCH2CH2CH3
acetone(common name), propanone
3-hexanone
cyclohexanone
Ethers
Compound in which an oxygen joins 2 hydrocarbon groups
Used as anaesthetic in hospital
Examples:
CH3CH2-O-CH2CH3
CH3-O-CH2CH2CH3
CH3
I
CH3C-CH2 CH2-O-CH3
I
Hospital ether, ethoxyethane
1-methoxypropane
1-methoxy-3,3-dimethylbutane
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CH3
Amines
Compound containing an NH2 group
Have “fish-like” odour
Examples
CH3-CH2-NH2
H2N-CH2-CH2 -CH2-CH2-NH2
CH3-CH-CH2--CH2-CH3
I
NH2
Aminoethane
1,4-diaminobutane
(putrescine, decomposing meat)
2-aminopentane
Amides
Compound containing a CONH2 group.
O
II
- C - NH2
Examples:
CH3-CO-NH2
CH3-CH2- CH2- CH2- CH2- CONH2
CH3
I
CH3-C- CH2- CONH2
I
CH3
ethanamide
hexanamide
3,3-dimethylbutanamide
Carboxylic Acids
Compound containing a COOH group
O
II
-C–O-H
Examples:
CH3COOH
HCOOH
CH3-CH2- CH2- COOH
Acetic acid (common name), ethanoic acid
Formic acid (common name), methanoic acid
Found in red ant venom, fourmis (French)
Butyric acid (common name), butanoic acid
Responsible for odour of smelly feet
Amino Acids
Compound that contains carboxylic acid and amine group
20 amino acids: building blocks essential to life
11
Example:
CH3- CH – COOH
2-aminopropanoic aicd (common name: alanine)
I
NH2
2 important properties p.237
a) highly soluble in water
b) link with other amino acids to form dipeptides and polypeptides forming proteins
O
O
O
O
II
II
II
II
H–N-CH2-C-OH + H-N-CH2-C-OH  H–N-CH2-C- N-CH2-C-OH + H2O
I
I
I
I
H
H
H
H
a “dipeptide”
Esters
Compound in which a COO group joins 2 hydrocarbon chains
Rule:
Hydrocarbon chain attached directly to carbon side of the COO group has its “e” ending
changed to “oate”. The C in the COO group is considered to be part of the parent hydrocarbon
chain
Hydrocarbon chain attached to oxygen side of the COO group is named as al alkyl group; the
name of the alkyl group id used as a separate, initial word.
Examples:
CH3 – CH2 – CH2 – COO- CH3
HCOO - CH2 – CH2 – CH2 – CH3
CH3 – CH2 – COO - CH2 – CH3
CH3 – COO - CH2- CH2 – CH3
methyl butanoate
butyl methanoate
ethyl propanoate
propyl ethanoate
Ester Preparation and Properties
Reaction an organic acid (carboxylic) and an alcohol in the presence of an inorganic scid such
as HCl or H2SO4.
Ethanoic acid
O
II
CH3 – C- O –H
methanol
+ HO - CH3

methyl ethanoate water
O
II
CH3 – C- O – CH3 + H2O
Lab experiment:
Few ml of carboxylic acid + few ml of alcohol + few drops of acid + heat
Result: distinct ester smell
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Ester
methyl butanoate
pentyl ethanoate
octyl ethanoate
Odour
Ester
pineapples pentyl propanoate
bananas
ethyl methanoate
orange rind
Odour
apricots
rum
Exercises Heb p.239 #34-36
D. Summary of Functional Groups
Heb p. 240
Exercises Heb p.240-4 #37-44
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