2 Alkanes

(1)

members different in molar mass is 14 g mol

members different in molar mass is 14 g mol-1-1

4.

4. StrucStructural tural formformulae ulae of aof alkanelkaness N

Naammee NNoo. . oof f isomers

isomers Structural formulae and NameStructural formulae and Name Methane Methane CH CH44 00 Ethane, Ethane, C C22HH66 00 Propane, Propane, C C33HH88 00 Butane, Butane, C C44HH1010 22 H H │ │ H ─ H ─ CC ─ H─ H │ │ H H H H HH │ │ ││ H ─ H ─ C ─ CC ─ C ─ H ─ H │ │ ││ H H HH H H H H HH │ │ │ │ ││ H ─ H ─ C ─ C ─ CC ─ C ─ C ─ H─ H │ │ │ │ ││ H H H H HH H H H H H H H H │ │ │ │ │ │ │ │ H ─ H ─ C ─ C ─ C ─ CC ─ C ─ C ─ C ─ H─ H │ │ │ │ │ │ │ │ H H H H H H H H n-butane n-butane

(2)

Pentane, Pentane, C C55HH1212 33 2

-2 - methmethyl propaneyl propane H H H H HH │ │ │ │ ││ H ─ H ─ C ─── C ─── CC ─── C ─── C ─ H─ H │ │ ││ ││ H H H─ H─ CC ─H H ─H H │ │ H H H H H H H H H H H H │ │ │ │ │ │ │ │ │ │ H ─ H ─ C ─ C ─ C ─ CC ─ C ─ C ─ C ─ ─ CC ─ H─ H │ │ │ │ │ │ │ │ │ │ H H H H H H H H H H n-pentane n-pentane H H H H H H HH │ │ │ │ │ │ ││ H ─ H ─ C ─── C ─── CC ─── C ─── C ─ C ─ C ─ H─ H │ │ ││ │ │ ││ H H H─ H─ CC ─H H H ─H H H │ │ H H

2-2-metmethylhyl butane butane

(3)

Hexane, Hexane, C C66HH1414 55 H H │ │ H H H ─ H ─ CC ─ H ─ H HH │ │ ││ ││ H ─ H ─ C ─── C ─── CC ─── C ─── C ─ H─ H │ │ ││ ││ H H H─ H─ CC ─H H ─H H │ │ H H 2,2-dimethyl propane 2,2-dimethyl propane H H H H H H H H H H H H │ │ │ │ │ │ │ │ │ │ │ │ H ─ H ─ C ─ C ─ C ─ CC ─ C ─ C ─ C ─ ─ CC ─ C ─ C ─ H─ H │ │ │ │ │ │ │ │ │ │ │ │ H H H H H H H H H H H H n-hexane n-hexane H H H H H H H H HH │ │ │ │ │ │ │ │ ││ H ─ H ─ C ─── C ─── CC ─── C ─── C ─ C ─ C ─ C ─ C ─ H─ H │ │ ││ │ │ │ │ ││ H H H─ H─ CC ─H H H H ─H H H H │ │ H H 2 - methyl pentane 2 - methyl pentane

(4)

H H │ │ H H H ─ H ─ CC ─ ─ H H H H HH │ │ ││ │ │ ││ H ─ H ─ C ─── C ─── CC ─── C ─── C ─ C ─ C ─ H─ H │ │ ││ │ │ ││ H H H─ H─ CC ─H H H ─H H H │ │ H H 2,2 - dimethyl butane 2,2 - dimethyl butane H H H H H H H H HH │ │ │ │ │ │ │ │ ││ H ─ H ─ C ─ C ─── CC ─ C ─── C ─── C ─── C ─ C ─ C ─ H─ H │ │ │ │ │ │ │ │ ││ H H H─ H H H─ CC ─H H H ─H H H │ │ H H 3 - methyl pentane 3 - methyl pentane H H │ │ H H H H H H ─ ─ CC ─H H ─H H │ │ ││ ││ ││ H ─ H ─ C ─── C ─── CC ─── C ─── C ─── C ─── C ─ H─ H │ │ ││ │ │ ││

(5)

Physical Properties

Physical properties of alkanes

i.

i. cannot

cannot conduct

conduct electrity

electrity

ii.

ii. less

less dense

dense than

than water

water

iii.

iii. dissolve

dissolve in

in organic

organic solvents,

solvents, insoluble

insoluble in

in water

water

iv

iv.. lo

low m

w mel

eltiting

ng an

and

d bo

boililin

ing

g po

poin

ints

ts

Conclusion:

- molecule held together by weak intermolecular forces

- properties of

- properties of covalent compound

covalent compound

- gradually steady increase as the number of carbon in

- gradually steady increase as the number of carbon in alkane

alkane

increases

(6)

6. Steps to name

6. Steps to name branched alkanes;branched alkanes; i.

i. determined determined and and named named the the long long chainschains ii.

ii. determined determined and and named named the the branch branch chainchain



 CHCH₃₃ :: methylmethyl 

 CC22HH55 OR OR   CHCH22CHCH33 : ethyl: ethyl 

 CC₃₃HH₇₇ OR OR   CHCH₂₂CHCH₂₂CHCH₃₃ : prophyl: prophyl iii.

iii. give number to give number to the carbon atthe carbon atoms in long coms in long chain, which hain, which startedstarted

from the nearest branched from the nearest branched

iv.

iv. The number for carbon atom which branched emerged from,The number for carbon atom which branched emerged from,

must put before/infront the alkyl must put before/infront the alkyl v.

v. NaNamemed td the he brbrananchched ed fifirstrst, f, folollolowewed by d by ththe ne namamed ed of of lolong ng chchaiainsns The word “

The word “ di, tridi, tri” is used if the branched chains is more than one” is used if the branched chains is more than one

Chemical Properties

Pg 38

Reactivity of alkanes

1. 1. Not reac

Not reactive/

tive/unrea

unreactive b

ctive becaus

ecausee

saturatedsaturated

hydrocarbon

2. 2. Did not dec

Did not decolou

olourized pu

rized purple solu

rple solution of

tion of

acidified potassiumacidified potassium

manganate(VII)

3. 3. Did not

Did not decolourized

decolourized reddish

reddish brown so

brown solution o

lution of f

bromin waterbromin water

4. 4. Ne

Neut

utra

ral.l.

Combustion of alkanes

1. 1. In

In th

thee

presence of sufficient oxygenpresence of sufficient oxygen

, alkanes burns to form

carbon dioxide and water. –

carbon dioxide and water. – complete combustion

complete combustion

Chemical equation:

(7)

ii. C

22

H

66

+

+ 7/2

7/2 O

O

22 

2CO

22

+

+ 3H

3H

22

O

iii. C

44

H

1010

+

+ 13/2

13/2 O

O

22 

4CO

22

+

+ 5H

5H

22

O

iivv.

.

C

66

H

1414

+ 19/2 O

22 

6CO

22

+

7H

22

O

Answers Answers

ii.. C

CH

H

44

+

+ 2O

2O

22 →→

CO

22

+

+ 2H

2H

22

O

ii. C

22

H

66

+

+ 7 O

7 O

22 

2CO

22

+

+ 3H

3H

22

O

2

2 2 x C

2 x C

22

H

66

+

+ 2

2 x

x 7

7 O

O

22 

2x 2CO

22

+ 2x

+

2x 3H

3H

22

O

2

2 2C

2C

22

H

66

+

+ 7 O

7 O

22 

4CO

22

+

+ 6H

6H

22

O

iiiiii.

.

C

44

H

1010

+

+ 13/2

13/2 O

O

22 

4CO

22

+

+ 5H

5H

22

O

iivv.

.

C

66

H

1414

+

+ 19/2

19/2 O

O

22 

6CO

22

+

+ 7H

7H

22

O

C

33

H

88

C

H

(8)

C

77

H

1616

C

88

H

1818

C

99

H

2020

C

1010

H

2222

2. 2. If

If there

there is

is insufficient oxygen

insufficient oxygen

, carbon monoxide or carbon

may be formed –

may be formed – incomplete combustion

incomplete combustion

i. CH

44

+ 3/2 O

22 

CO + 2H

22

O

2CH

44

+

+ 3 O

3 O

22 

2CO + 4H

22

O

ii. CH

44

+

+ O

O

22 

C + 2H

22

O

Halogenation

1.

1. The reaction is betweenThe reaction is between alkane dan chlorinealkane dan chlorine..

2.

2. Takes place under Takes place under sunlight/ultra violet lightsunlight/ultra violet light..

3.

3. Carbon-hydrogen bonds brokenCarbon-hydrogen bonds broken and newand new carbon-halogen bondscarbon-halogen bonds

are formed

are formed. One or more hydrogen atoms in alkanes molecule may be. One or more hydrogen atoms in alkanes molecule may be subtituted by halogen.

subtituted by halogen. 4. Halogenation is

4. Halogenation is substitution reactionsubstitution reaction..

One atom or a group of atoms in a molecule is replaced by another atom or group of

atoms. atoms. Chlorination of methane Chlorination of methane First stage; First stage;

(9)

Second stage; Second stage; Third stage ; Third stage ; Fourth stage; Fourth stage;

Overall equation/chemical equation

CH CH44 + 4Cl+ 4Cl22 CClCCl44 + 4HCl+ 4HCl

HW:

HW: PG41

PG41 EP B

EP B no.

no. 1-3

1-3

Prepared; Prepared; H H ClCl │ │ || H ─ H ─ CC ─ ─ Cl + Cl + ClCl22 → → H — H — CC — — Cl Cl + + HClHCl │ │ || H H H H dichloromethanedichloromethane Cl Cl Cl Cl │ │ || H ─ H ─ CC ─ ─ Cl + Cl + ClCl22 → → H — H — CC — — Cl Cl + + HClHCl │ │ || H H Cl Cl trichloromethanetrichloromethane Cl Cl Cl Cl │ │ || H ─ H ─ CC ─ ─ Cl + Cl + ClCl22 → Cl → Cl — — CC — — Cl Cl + + HClHCl │ │ || Cl Cl Cl Cl tetrachloromethatetrachloromethanene