Naming Of Smaller Compounds

GOC of Class 11

Naming Of Smaller Compounds

We shall take up the cases family wise. The first family is hydrocarbon. But it is a big family. For the sake of convenience it has been divided into three sub−groups.

(i) Saturated hydrocarbons having (C − C) bond.

(ii) Unsaturated hydrocarbons having (C = C) bond and

(iii) Unsaturated hydrocarbons having (C ≡C) bond.

In IUPAC rule, the last part in the name designates the family of the compound and the first part of the name indicates the number of carbon atoms in the parent chain of the compound.

(i) Hydrocarbons with only (C−C) bond

The first family is hydrocarbon having (C − C) bond and H atoms. This family has been given the name alkane. So the name of all saturated hydrocarbons end in −ane.

The name of the alkanes is given by writing the number of carbon atoms as prefix followed by suffix −ane.

Common name	Molecular formula	IUPAC name
Methane	CH₄	Methane
Ethane	C₂H₆	Ethane
Propane	C₃H₈	Propane
Butane	C4H₁₀	Butane
Pentane	C₅H12	Pentane
Hexane	C₆H₁₄	Hexane
Heptane	C₇H₁₆	Heptane
Octane	C₈H₁₈	Octane
Nonane	C₉H₂₀	Nonane
Decane	C₁₀H₂₂	Decane

Naming of alkyl radicals

When one hydrogen atom is removed from an alkane, the radical or group formed is called alkyl radical or group. The IUPAC name is given to such radicals by replacing −ane of alkane by −yl. Thus

−CH₃ is called methyl (Me)

−C₂H₅ is called ethyl (Et)

CH₃− CH₂− CH₂is called n−propyl (n−Pr)

(CH₃)₂−C is called tertiary butyl or t−butyl (t–But)

(ii) Hydrocarbons with only (C = C) bond

The suffix of this family is −ene.

Common name	Molecular formula	IUPAC name
Ethylene	C2H4	Ethene
Propylene	C₃H₆	Propene
Butylene	C₄H₈	Butene
Pentylene	C₅H₁₀	Pentene
Hexene	C₆H₁₂	Hexene
Heptene	C₇H₁₄	Heptene
Octene	C₈H₁₆	Octene

(iii) Hydrocarbons with only (C ≡ C) bond

The suffix of this family is −yne.

Common name	Molecular formula	IUPAC name
Acetylene	C₂H₂	Ethyne
Methyl acetylene	C₃H₄	Propyne
Dimethyl acetylene	C₄H₆	Butyne
Ethyl methyl acetylene	C₅H₈	Pentyne
Hexyne	C₆H₁₀	Hexyne
Heptyne	C₇H12	Heptyne
Octyne	C8H₁₄	Octyne

(iv) Alcohol

The suffix of this family is −ol. So the general name ALKANOL.

Common name	Molecular formula	IUPAC name
Methyl alcohol	CH₃OH	Methanol
Ethyl alcohol	CH₃CH₂OH	Ethanol
Propyl alcohol	CH₃CH₂CH₂OH	Propanol
Butyl alcohol	CH₃CH₂CH₂CH₂OH	Butanol
Pentanol	CH₃CH₂CH₂CH₂CH₂OH	Pentanol
Hexanol	CH₃CH₂CH₂CH₂CH₂CH₂OH	Hexanol

(v) Ether

This compound is treated as the alkoxy derivative of alkane, so the word ALKOXY is written before the name of parent hydrocarbon.

R−O − R’

alkoxy alkane (where R = Smaller alkyl group; R’ = Bigger parent alkyl group)

IUPAC name: ALKOXY ALKANE

Common name	Molecular formula	IUPAC name
Dimethyl ether	CH₃− O − CH₃	Methoxy methane
Ethyl methyl ether	CH₃− O − C₂H₅	Methoxy ethane
Diethyl ether	C₂H₅− O – C₂H₅	Ethoxy ethane

(vi) Aldehyde

The suffix of family is −al.

Common name	Molecular formula	IUPAC name
Formaldehyde	HCHO	Methanal
Acetaldehyde	CH₃CHO	Ethanal
Propionaldehyde	CH₃CH₂CHO	Propanal
Butyraldehyde	CH₃CH₂CH₂CHO	Butanal
Pentanal	CH₃CH₂CH₂CH₂CHO	Pentanal
Hexanal	CH₃CH₂CH₂CH₂CH₂CHO	Hexanal

(vii) Ketone

The suffix of family is −one.

Common name	Molecular formula	IUPAC name
Acetone	CH₃COCH₃	Propanone
Ethyl methyl ketone	CH₃COC₂H₅	Butanone
Diethyl ketone	C₂H₅COC₂H₅	Pentanone
Hexanone	C₂H₅COC₃H₇	Hexanone
Heptanone	C₃H₇COC₃H₇	Heptanone

(viii) Acid

The suffix of family is −oic acid.

Common name	Molecular formula	IUPAC name
Formic acid	HCOOH	Methanoic acid
Acetic acid	CH3COOH	Ethanoic acid
Propionic acid	CH₃CH₂COOH	Propanoic acid
Butanoic acid	CH₃CH₂CH₂COOH	Butanoic acid
Pentanoic acid	CH₃CH₂CH₂CH₂COOH	Pentanoic acid

(ix) Amines

There are three types of amines−primary, secondary and tertiary

Primary amines are named by putting the word Amino before alkane.

The title of primary amine is Aminoalkane.

Secondary amines are named by putting the word Alkylamino before alkane.

The title of secondary amine is Alkylaminoalkane.

Tertiary amines are named by putting the word Dialkylamino before alkane.

The title of tertiary amine is Dialkylaminoalkane.

Common name	Molecular formula	IUPAC name
Methyl amine	CH₃NH₂	Amino methane
Ethyl amine	CH₃CH₂NH₂	Amino ethane
Dimethyl amine	CH₃ − NH − CH₃	N−Methyl amino methane
Trimethyl amine	(CH₃)₂N − CH₃	N,N−Dimethyl amino methane

(x) Derivatives of Acid

(a) Ester: The IUPAC name of ester is ALKYL ALKANOATE.

Naming Of Smaller Compounds

Common name	Molecular formula	IUPAC name
Methyl formate		Methyl methanoate
Methyl acetate		Methyl ethanoate

(b) Amide: The IUPAC name is ALKANAMIDE.

Examples:

Common name	Molecular formula	IUPAC name
Formamide	HCONH₂	Methanamide
Acetamide	CH₃CONH₂	Ethanamide
Propionamide	CH₃CH₂CONH₂	Propanamide

(c) Acid chloride: The IUPAC name is ALKANOYL CHLORIDE.

Examples:

Common name	Molecular formula	IUPAC name
Formyl chloride	HCOCl	Methanoyl chloride
Acetyl chloride	CH₃COCl	Ethanoyl chloride
Propionyl chloride	CH₃CH₂COCl	Propanoyl chloride

(d) Acid Anhydride: The IUPAC name is ALKANOIC ANHYDRIDE.

To name a mixed anhydride alphabetical order is maintained.

Common name	Molecular formula	IUPAC name
Acetic anhydride	CH₃−CO−O−CO−CH₃	Ethanoic anhydride
Propionic anhydride	C₂H₅−CO−O−CO−C₂H₅	Propanoic anhydride
Acetic propionic anhydride	CH₃−CO−O−CO−C₂H₅	Ethanoic propanoic anhydride