Alkane

Alkane

The aliphatic hydrocarbons which have carbon-carbon single bond are called alkane.

The general formula of alkane is C_nH_2n+2, where n = number of hydrogen

E.g. methane (CH₄), ethane (C₂H₆) etc.

Word root Alkane Formula

C₁ → Meth Methane CH₄

C₂ → Eth Ethane C₂H₆

C₃ → Prop Propane C₃H₈

C₄→ But Butane C₄H₁₀

C₅ → Pent Pentane C₅H₁₂

C₆ → Hex Hexane C₆H₁₄

C₇ → Hept Heptane C₇H₁₆

C₈ → Oct Octane C₈H₁₈

C₉ → Non Nonane C₉H₂₀

C₁₀ → Dec Decane C₁₀H₂₀

The suffix of the alkane is (ane).

Alkyl

The replacement or loss of one hydrogen from the alkane is called alkyl.

It is denoted by (-R), where –R indicates alkyl group.

The general formula of the alkyl is C_nH_2n+1.

Nomenclature

CH₄ → methane

C₂H₆ → Ethane

CH₃ - CH₃ → Ethane

C₃H₈ → Propane

CH₃ - CH₂ - CH₃ → n-propane

CH₃ - CH₂ - CH₂ - CH₂ - CH₃ → n-pentane

IUPAC Nomenclature

Prefix + word root + primary suffix + secondary suffix

Prefix → 3-methyl

Word root → Hex

Primary suffix → ane

Therefore the IUPAC name is 3-methyl hexane

Prefix → 4- ethyl 4,6- methyl

Word root → Oct

Primary suffix → ane

Prefix

-CH₃ → Methyl

-C₂H₅ → Ethyl

-Cl → Chloro

-Br → Bromo

-I → Iodo

-F → Fluoro

-CO → Keto

-CHO → Aldo

-NH₂ → Amino

-OH → Hydroxyl

-CN → Cyano

-NO₂ → Nitro

3-bromo 2, 4, 4 –trichloro 3-iodo 2-methyl hexane

Note:

R-X → alkyl halide or haloalkane

X = Cl, Br, I, F

CH₃-Cl

Chloromethane Or Methyl Chloride

CH₃-CH₂-CH₂-Br

Bromo Propane Or Propyl bromide

Isomerism

The organic compounds having same molecular formula but different structural formula are called isomers and the phenomenon is called isomerism.

From butane isomers, occur i.e. methane, ethane, propane does not have isomers.

E.g. pentane (C₅H₁₂)

Functional group

The structure of the particular family of an organic compound is called functional group.

It determines the properties of the organic compound.

S.n	Class	General formula	Functional group	Secondary suffix
1	Hydrocarbon
a.	Alkane	CnH2n+2
b.	Alkene	CnH2n
c.	Alkyne	CnH2n-2
2	Alkyl halide	R-X	-X
3	Alcohol	R-OH	-OH	Ol
4	Ether	R-O-R	-O-	ether
5	Aldehyde	R-COH	-COH	al
6	Ketone	R-CO-R	-CO-	one
7	Carboxylic acid	R-COOH	-COOH	oic acid
8	Ester	R-COO-R	-COO-	ester
9	Amide	R-CONH2	-CONH2	amide
10	Amine	R-NH2	-NH2	amine
11	Cyanide	R-CN	-CN	nitril

Priority order: COOH > CHO > CO > OH

Alcohol

Structure: R - OH

Functional group: -OH

Secondary suffix: ol

Alkane – e + ol → alkanol

E.g. CH₃ - CH = CH - CH₂ - OH → but-2-ene-1-ol

CH₃ - CH₂ - CH₂ - OH → Propanol

Aldehyde

Structure: R - CHO

Functional group: -CHO

Secondary suffix: al

Alkane – e + al → alkanol

E.g. CH₃ - COH → Ethanal

CH₃ - CH₂ - COH → Propanal

H - CHO →Methanal

Note:

OCH₃ → Methoxy

OC₂H₅ → Ethoxy

OC₃H₇ → Propoxy

Carboxylic acid

Structure: R - COOH

Functional group: -CHO

Secondary suffix: oic acid

Alkane – e + oic acid → alkanoic acid

E.g. H - COOH → Methanoic acid

CH₃ - COOH → Ethanoic acid

CH₃ - CH₂ - COOH → Propanoic acid

CH₃ - CH₂ - CH₂ - COOH →Butanoic acid

Ketone

Structure: R – COO - R

Functional group: -COO-

Secondary suffix: one

Alkane – e + one → alkanone

E.g.

→ Propane – e + one i.e propanone or propan – 2 – one

Amine

Structure: R - NH₂

Functional group: -NH₂

Secondary suffix: amine

Alkane – e + amine = alkanamine

E.g. CH₃-NH₂ → Methenamine

CH₃ - CH₂ - NH₂ → Ethanamine

Ether

Structure: R - O - R

Functional group: - O -

Secondary suffix: Ether

E.g. CH_3­ - O - CH₃ → dimethyl ether/methoxy methane

CH₃ - CH₂-O - CH₃ →methoxy ethane

Cyanide

Structure: R - CN

Functional group: -CN

Secondary suffix: nitril

E.g. CH₃ - CN →methyl cyanide/ethane nitril

CH₃ - CH₂ - CH₂ - CN →butane nitril/propyl cyanide

Amide

Structure: R - CONH₂

Functional group: -CONH₂

Secondary suffix: amide

Alkane – e + amide = alkanamide

E.g.

O

‖

CH₃ - C - NH₂ → Ethanamide

Reference

Pulse, Tracy. Introduction to chemistry. u.s.a: flexbook, 2010.

Pathak, Sita Karki. The Text Book of Chemistry. Kathmandu: Vidhyarthi Pustak Bhandar, 2012.