2023/3/29 15:19
O ganic Chemi
F ndamen a s of organic chemis r
“A homo ogous series is a series of compounds of the same fami y, with the same genera
formu a, which differ from each other by a common structura unit.”
“Structura formu as can be represented in fu and condensed format.”
“Structura isomers are compounds with the same mo ecu ar formu a but different arrangements
of atoms.”
“Func ona groups are the reac ve parts of mo ecu es.”
“Saturated compounds contain sing e bonds on y and unsaturated compounds contain doub e
or trip e bonds.”
“Benzene is an aroma c, unsaturated hydrocarbon.”
F nc ona gro p chemis r
A kanes:
“A kanes have ow reac vity and undergo free-radica subs tu on reac ons.”
A kenes:
“A kenes are more reac ve than a kanes and undergo addi on reac ons. Bromine water
can be used to dis nguish between a kenes and a kanes.”
A coho s:
“A coho s undergo nuc eophi ic subs tu on reac ons with acids (a so ca ed esterifica on
or condensa on) and some undergo oxida on reac ons.”
Ha ogenoa kanes:
“Ha ogenoa kanes are more reac ve than a kanes. They can undergo (nuc eophi ic)
subs tu on reac ons. A nuc eophi e is an e ectron-rich species containing a one pair that
it donates to an e ectron-deficient carbon.”
Po ymers:
“Addi on po ymers consist of a wide range of monomers and form the basis of the
p as cs industry.”
Benzene:
“Benzene does not readi y undergo addi on reac ons but does undergo e ectrophi ic
subs tu on reac ons.”
A homo ogous series is a fami y of compounds that are c ose y re ated.
The different characteris cs of a homo ogous series inc ude:
Members have a func ona group.
h p ://
.bli no e .o g/ib/chemi
/o ganic-chemi
.h ml#fo m la -of-compo nd
1/11
2023/3/29 15:19
O ganic Chemi
Mo ar mass of consequent members differ by 14
J
1
.
Consequent members differ by CH2 group.
Members show a gradua trend in physica proper es.
Members have simi ar chemica proper es.
Different homo ogous series exist, such as a kanes, a kenes, a coho s, etc.
Empirica formu a:
An empirica formu a is the simp est who e-number ra o of atoms in a compound.
Mo ecu ar formu a:
The mo ecu ar formu a represents the rea number of atoms and each type of atom in a
compound.
Structura formu ae:
There are two types of structura formu ae:
Fu structura formu ae:
A atoms and bonds between a atoms are shown.
Condensed structura formu ae:
Assumes certain bonds and therefore a atoms need not be shown.
Easier to draw.
Ske eta formu ae:
removes a atoms, eaving on y a ‘ske eton’ of the mo ecu e.
Stereochemica formu ae:
shows the three-dimensiona posi ons of atoms around a carbon.
NOTE: When the exact detai s of the hydrocarbon need not be shown, we abbreviate that part of the
mo ecu e to R. For benzene-ring containing mo ecu es that are a so known as aroma c compounds, a
different symbo is used to show the ring.
Func ona group: sing e or groups of atoms that dictate the proper es of a group of organic
compounds.
A kanes
Func ona group: a ky .
Saturated compound.
Genera formu a: C
H2
+2 .
Naming a kanes
[ e ] + a e.
For examp e: propane, butane, methane, etc.
A kenes
Func ona group: a keny (doub e carbon bond).
Known as an unsaturated compound.
Genera formu a: C
H2 .
Naming a kenes
[ e ] + e e.
For examp e: hexene, butene, etc.
h p ://
.bli no e .o g/ib/chemi
/o ganic-chemi
.h ml#fo m la -of-compo nd
2/11
2023/3/29 15:19
O ganic Chemi
A kynes
Func ona group: a kyny (trip e carbon bond).
Known as a saturated compound.
Genera formu a: C
H2
2.
Naming a kynes
[ e ]+
e.
For examp e: butyne, propyne, etc.
Ha ogenoa kanes
Formed when a ha ogen is bonded to an a ky group.
Func ona group: R
Genera formu a: C
X (R being the a ky group and X being any ha ogen).
H2 +1 X .
Naming ha ogenoa kanes
c
-/b
-/ d - + [a a e].
For examp e: Bromoethane, iodobutane, etc.
A coho s
Func ona group: OH (hydroxy group).
Genera formu a: C
H2
+1 OH .
Naming a coho s
[ e ]+
.
For examp e: propano , decano , etc.
A dehydes
Func ona group: CHO (a dehyde group)
Genera formu a: C
H2
+1 CHO .
Naming a dehydes
[ e ]+a.
For examp e: butana , pentana .
Ketones
Func ona group:
Genera formu a: C
CO (ketone)
H2 +1 COC H2
+1 (where
and
are two posi ve integers).
Naming ketones
[ e ]+a
e.
For examp e: ethanone, hexanone, etc.
Carboxy ic acids
Func ona group:
Genera formu a: C
h p ://
COOH (carboxy ).
H2 +1 COOH .
.bli no e .o g/ib/chemi
/o ganic-chemi
.h ml#fo m la -of-compo nd
3/11
2023/3/29 15:19
O ganic Chemi
Naming carboxy ic acids
[ e ]+
c ac d.
For examp e: propanoic acid, butanoic acid, etc.
Ethers
O (ether).
Genera formu a: C H2 +1 OC H2
Func ona group:
+1 (where
and
are two posi ve integers).
Naming ethers
[ e
e ca b
c a ]+
+[ e
e ca b
c a ] + a e.
For examp e: methoxypropane, ethoxyethane, etc.
Esters
Func ona group:
Genera formu a: C
COO (ester).
H2 +1 COOC H2
+1 (where
and
are two posi ve integers).
Naming esters
[ e
ac
]+
+[ e
ca b
c ac d] +
a e.
Amines
Func ona group:
Genera formu a: C
N H2 .
H2 +1 N H2 .
Naming amines
Primary amines
Contain on y one carbon connected to the nitrogen in the compound.
[ e ]+a
e.
For examp e: propanamine, butanamine, etc.
Secondary amines
Contain two carbons connected to the nitrogen in the compound.
N-[ e
e ca b
c a ]+
+[ e
e ca b
c a +a
e.
For examp e: N-methy butanamine, N-ethy propanamine, etc.
Ter ary amines
Contain three different carbon bonds connected to the nitrogen in the compound.
N-[ e
e
ca b
c a ]+
+ N-[ e
e ca b
c a ]+
+[ e
e
ca b
c a +a
For examp e: N, N - diethy propanamine, N-propy -N-buty hexanamine.-
Amides
Func ona group:
Genera formu a: C
CON H2 (carboxamide or amido).
H2 +1 CON H2 .
Naming amides
Primary amides:
Contain on y one carbon bonded to the nitrogen.
[ e ]+a
de.
For examp e: butanamide, propanamide, etc.
Secondary amides:
Contain two carbon atoms bonded to the nitrogen.
h p ://
.bli no e .o g/ib/chemi
/o ganic-chemi
.h ml#fo m la -of-compo nd
4/11
2023/3/29 15:19
O ganic Chemi
N-[ e
e ca b
c a ]+
+[ e
e ca b
c a +a
de.
For examp e: N-buty hexanamide, N-propy pentanamide, etc.
Ter ary amides
Contain three different carbon bonds connected to the nitrogen in the compound.
N-[ e
e
ca b
c a ]+
+ N-[ e
e ca b
c a ]+
+[ e
e
ca b
c a +a
d
For examp e: N, N - diethy propanamide, N-propy -N-buty hexanamide.
Nitri es
Func ona group:**
Genera formu a: C
CN (nitri e)
H2 +1 CN .
Naming nitri es
The carbon from the nitri e group counts as the first carbon of the chain.
[ e ]+a e+
e.
For examp e: ethanenitri e, propanenitri e.
Are es
Func ona group: pheny
Genera formu a: C6 H5 .
Prefix: -
e
or Suffix: -be
e e.
Acidic and basic func ona groups
Some func ona groups act ike Brønsted-Lowry acids and bases. The carboxy acid func ona
group (-COOH) can donate a proton to form the carboxy ate ion (R-COO ).
Compounds such as those containing the amine func ona group can use the one pair from the
nitrogen atom to accept a proton.
Structura isomerism
Structura isomers are compounds with the same mo ecu ar formu a but a different structure and
arrangement of atoms.
Structura isomers occur when a mo ecu e can have its func ona group in different posi ons in the
mo ecu e or when it can a ter its ongest carbon chain, and these isomers are a so known as chain
isomers.
Structura isomerism can a so occur when a mo ecu e has the same mo ecu ar formu a but two
different func ona groups, which is known as func ona group isomerism.
Structura isomers have the simi ar chemica proper es but different physica proper es such as
me ng and boi ing points.
Vo a ity
Vo a ity is defined as how fast a mo ecu e evaporates and is determined by the mo ecu e’s boi ing
point.
There are three factors that influence the vo a ity and boi ing point of a substance.
Mo ar mass:
As mo ar mass
h p ://
.bli no e .o g/ib/chemi
/o ganic-chemi
.h ml#fo m la -of-compo nd
5/11
2023/3/29 15:19
O ganic Chemi
Strength of London Dispersion forces
Energy required to break the intermo ecu ar bonds between a mo ecu e
Boi ing point
Surface area:
Branch-chained isomers have a sma er surface area and so they have ess contact with other
mo ecu es.
Strength of London Dispersion forces
compared to straight-chain isomers.
Energy required to break the intermo ecu ar bonds between a mo ecu e .
Boi ing point .
Nature of func ona group:
Po ar func ona groups resu t in stronger dipo e-dipo e interac ons and therefore require
higher amounts of energy to break the bonds, eading to higher boi ing points.
Some mo ecu es, such as a coho s and carboxy ic acids can form hydrogen bonds and therefore
have even higher boi ing points.
Some organic compounds, such as a coho s, ha ogenoa kanes, amides, and amines are c assified into
primary, secondary, and ter ary compounds.
A coho s
Primary a coho s have on y one carbon atom direct y bonded to carbon that is bonded to the
func ona group.
Secondary a coho s have two carbon atoms direct y bonded to carbon that is bonded to the
func ona group.
Ter ary a coho s have three carbon atoms direct y bonded to carbon that is bonded to the
func ona group.
Ha ogenoa kanes
Primary, secondary, and ter ary ha ogenoa kanes have simi ar characteris cs to primary, secondary,
and ter ary a coho s.
Amides and amines
Primary amides and amines have on y one carbon atom direct y bonded to the amide or amine
func ona group.
Secondary amides and amines have two carbon atoms direct y bonded to the amide or amine
func ona group.
Ter ary amides and amines have three carbon atoms direct y bonded to the amide or amine
func ona group.
Arenes are aroma c hydrocarbons. They have the pheny func ona group. The simp est form of an
arene is benzene, ike C6 H6 . Benzene has two resona ng structures, meaning that a
bonds in
the benzene mo ecu e are intermediate between 1 and 2.
These resonance structures are known as Keku
structures since they were proposed by the chemist
Friedrich August Keku .
However, evidencce emerged sugges ng that these structures were not accurate.
The first piece of evidence is given by the carbon-carbon bond engths. A carbon-carbon bond
engths are exact y the same. If benzene contained a terna ng sing e and doub e bonds, it wou d
h p ://
.bli no e .o g/ib/chemi
/o ganic-chemi
.h ml#fo m la -of-compo nd
6/11
2023/3/29 15:19
O ganic Chemi
have a terna ng onger and shorter bond engths. Instead, the ength is between sing e and doub e
bonds, meaning its intermediate.
The second piece of evidence is that the there is on y one isomer for benzene. If benzene had three
carbon doub e bonds, that means it wou d have had more isomers, which it doesn’t. This is further
evidence that it does not have carbon doub e bonds.
The third piece of evidence is the reac ve nature of benzene. If benzene had doub e bonds, it wou d
undergo addi on reac ons ike a kenes or a kynes. However, it on y undergoes subs tu on.
The fourth and fina evidence is the entha py of hydrogena on of benzene. If the entha py of
hydrogena on was ca cu ated using theore ca va ues, it is ca cu ated to be more nega ve than the
experimenta , or actua va ue. The theore ca va ue is given by
360 J
1
, however, the
1
.
208 J
This difference in the entha py va ues, 152 J
experimenta va ue is given by
1
, known as resonance energy, suggests that the
actua structure of benzene is more stab e than the Keku
structure (since more energy was taken
in to break the bonds of the benzene mo ecu e).
The actua structure of benzene is different, which is shown in the image be ow.
Taken from h ps://hyungi022 .wordpress.com/2013/0 /12/a2-chemistry-a -about-benzene-ring/
The de oca ised e ectrons are shown as a circ e in the midd e of a hexagon structure.
Since a kanes are saturated hydrocarbons, they undergo subs tu on reac ons.
They are re a ve y unreac ve for two reasons:
carbon-hydrogen bond is non-po ar which means it is more stab e since charge distribu on is
not unequa .
Combus on reac on
A kanes undergo combus on in the presence of oxygen. They undergo two types of combus on:
Comp ete combus on
This occurs in the presence of excess oxygen.
C3 H8 ( ) + 5O2 ( )
3CO2 ( ) + 4H2 O( )
It resu ts in carbon dioxide and water.
Incomp ete combus on
h p ://
.bli no e .o g/ib/chemi
/o ganic-chemi
.h ml#fo m la -of-compo nd
7/11
2023/3/29 15:19
O ganic Chemi
This occurs in the presence of insufficient oxygen.
C3 H8 ( ) + 7O2 ( )
6CO( ) + 8H2 O( )
It resu ts in the forma on of carbon monoxide/carbon and water.
Free-radica subs tu on reac ons
A kanes react with ha ogens in free-radica subs tu on reac ons.
The condi on for this reac on is UV ight.
The reac on can be divided into 3 parts.
Ini a on
In this step, the ch orine (or any ha ogen) undergoes photochemica homo y c bond fission and
forms radica s of ch orine, which are very reac ve.
C
2C
2
Propaga on
In this step, the free-radica ch orine reacts with an a kane to form an a kane radica .
This a kane radica reacts with a ch orine free-radica again to form a ha ogenoa kane.
C +CH4
CH3 +C 2
CH3 +HC
CH3 C + C
The net amount of radica s remains the same as a radica is used and a radica is produced in every
reac on.
Termina on
In this step, two free-radica s combine again to form the origina mo ecu es and new mo ecu es.
A free-radica s are terminated.
C
CH3 +CH3
+C
C2
C2 H6 CH3 C
CH3 C
A kenes are unsaturated and undergo addi on reac ons where the doub e-bond is broken.
In addi on reac ons, two sma er mo ecu es react to form one bigger mo ecu e.
Hydrogena on
Hydrogena on occurs when an a kene reacts with hydrogen to form an a kane.
The condi ons for this reac on are N and 150
C.
C2 H 4 + H 2
C2 H 6
Ha ogena on
Ha ogena on occurs when an a kene reacts with a ha ogen gas.
C2 H 4 + B
2
C2 H 4 B
2
Hydrogen ha ides
Hydrogen ha ides react with a kenes to form ha ogenoa kanes.
h p ://
.bli no e .o g/ib/chemi
/o ganic-chemi
.h ml#fo m la -of-compo nd
8/11
2023/3/29 15:19
O ganic Chemi
C2 H4 + HB
C 2 H5 B
Hydra on
A kenes react with water to form a coho s.
The condi ons for this reac on are steam and concentrated H2 SO4 .
C2 H 4 + H 2 O
C2 H5 OH
Po ymerisa on
Po ymerisa on occurs when many a kenes join to form a po ymer.
A coho s are saturated and undergo subs tu on reac ons as we as some other reac ons.
Combus on of a coho s
A coho s, in excess oxygen, combust to form carbon dioxide and water.
2CH3 OH + 3O2
2CO2 + 4H2 O
Oxida on of a coho s
A coho s can be oxidised by oxidising agents such as acidified potassium dichromate (C 2 O72 ),
which is accompanied with a co or change from orange to green as it is reduced to C 3+ .
Depending on the type of a coho , different products are formed.
Primary a coho s
Primary a coho s undergo par a oxida on to form an a dehydes, a er which they form a carboxy ic
acid.
For these reac ons, heat under reflux (to a ow the a coho and the oxidising agent to remain in
contact for a onger me) is required with an excess of the oxidising agent.
Secondary a coho s
Secondary a coho s form a ketone.
The condi ons for this reac on are heat under reflux with a suitab e oxidising agent.
Ter ary a coho s
Since they have no hydrogen atom direct y bonded to the carbon atom that is bonded to the
func ona group, they do not undergo oxida on.
Esterifica on
Esters are formed when an a coho reacts with a carboxy ic acid.
In the name of the compound, the a ky group of the a coho comes first and the a ky group of the
carboxy ic acid comes second.
So, methano and propanoic acid wou d form methy propanoate.
h p ://
.bli no e .o g/ib/chemi
/o ganic-chemi
.h ml#fo m la -of-compo nd
9/11
2023/3/29 15:19
O ganic Chemi
Ha ogenoa kanes undergo subs tu on reac ons.
A nuc eophi e is a species that is rich in e ectrons and has a one pair of e ectrons, which means it is
a racted to mo ecu es with posi ve charge.
Nuc eophi ic subs tu on reac on to form a coho
In the ha ogenoa kane mo ecu e, the ha ogen is a nuc eophi e due to the three one pairs that it has.
So, the carbon (which has a par a posi ve charge in the bond) undergoes hetero y c bond fission
with the ha ogen where the ha ogen takes the bonding e ectrons.
In genera , in hetero y c bond fission, a bond breaks and one atom takes both the bonding e ectrons
from the cova ent bond. This forms opposite y charged ions.
The reac on that takes p ace is known as a nuc eophi ic subs tu on reac on as the nuc eophi ic
ha ogen is separated from the ha ogenoa kane and rep aced by another nuc eophi ic ion.
The nuc eophi ic ha ogen gains a nega ve charge a er being separated as it takes both the bonding
e ectrons.
Strong bases or a ka is ike NaOH are reacted with ha ogenoa kanes as they contain a nuc eophi ic
species, OH , which has a one pair of e ectrons (hence nuc eophi ic).
The OH ion subs tutes the ha ogen, and the ha ogenoa kane is converted to an a coho .
The reac on condi ons for the conversion of a ha ogenoa kane to an a coho are heat and a di ute
so u on of sodium or potassium hydroxide.
CH3 CH2 CH2 C + N aOH
CH3 CH2 CH2 OH + N aC
As seen by the reac on, the ha ogenoa kane 1-ch oropropane is converted to the primary a coho
propano with the by-product of sodium ch oride as ch orine is subs tuted for OH .
Benzene undergoes subs tu on reac ons to maintain its stab e structure.
The ring of de oca ised e ectrons in benzene represent a region of e ectron density.
Therefore, e ectrophi ic species are a racted to benzene due to its ring of de oca ised e ectrons.
So, benzene undergoes e ectrophi ic subs tu on reac ons.
An e ectrophi e is an e ectron-deficient species that has a par a posi ve or comp ete y posi ve
charge.
Nitra on
Benzene reacts with the nitronium ion (NO+
2 ) in an e ectrophi ic subs tu on reac on to form
nitrobenzene.
In this reac on, the nitronium ion acts as the e ectrophi e.
The cata yst for this reac on is concentrated su furic acid (H2 SO4 ).
Ha ogena on
Benzene a so undergoes e ectrophi ic subs tu on reac ons with ha ogens.
For examp e, ch orine reacts with benzene to form ch orobenzene and hydrogen ch oride. The
cata yst for this reac on is a uminium ch oride.
In genera , ha ogens react with benzene to form c
-,
-,
d -, b
- be e e with
the byproduct of a hydrogen ha ide (the ha ide that benzene reacted with). The cata yst, in genera ,
wi be a uminium ha ide (the ha ide that reacted with benzene).
Combus on of benzene
Like a hydrocarbons, benzene a so undergoes combus on in the presence of excess oxygen.
2C6 H6 + 15O2
h p ://
.bli no e .o g/ib/chemi
/o ganic-chemi
12CO2 + 6H2 O
.h ml#fo m la -of-compo nd
10/11