Match each type of organic isomerism on the left with its corresponding example pair of co… — JAMB UTME

Match each type of organic isomerism on the left with its corresponding example pair of compounds on the right.

Chain isomerismButane and $2$ -methylpropane
Positional isomerismButan- $1$ -ol and butan- $2$ -ol
Functional group isomerismEthanoic acid and methyl methanoate
Geometric isomerism $cis$ -But- $2$ -ene and $trans$ -but- $2$ -ene

Answer

Chain isomerism pairs with butane and

2

-methylpropane; Positional isomerism pairs with drop-in pair butan-

1

-ol and butan-

2

-ol; Functional group isomerism pairs with ethanoic acid and methyl methanoate; Geometric isomerism pairs with

cis

-but-

2

-ene and

trans

-but-

2

-ene.

Each type of isomerism is matched to its definitive structural characteristic: chain isomerism involves skeleton branching changes (butane and

2

-methylpropane), positional isomerism involves relocations of the same functional group (butan-

1

-ol and butan-

2

-ol), functional group isomerism involves different organic families sharing a formula (ethanoic acid and methyl methanoate), and geometric isomerism involves spatial orientations across a double bond (

cis

-but-

2

-ene and

trans

-but-

2

-ene).

Step-by-Step Solution

Analyze the carbon skeletons of butane and

2

-methylpropane.

Both have formula

C_4H_{10}

, but one is unbranched while the other is branched, defining chain isomerism.

Chain isomers possess identical molecular formulas but different carbon chain arrangements.

Examine the functional group positions in butan-

1

-ol and butan-

2

-ol.

The

-\text{OH}

group is on carbon-

1

in butan-

1

-ol and carbon-

2

in butan-

2

-ol, defining positional isomerism.

Positional isomers have the same functional group located on different carbon atoms along the same parent chain.

Compare the functional groups of ethanoic acid and methyl methanoate.

Ethanoic acid is a carboxylic acid (

CH_3COOH

) while methyl methanoate is an ester (

HCOOCH_3

). Both have the formula

C_2H_4O_2

, defining functional group isomerism.

Functional group isomers share a molecular formula but belong to different organic homologous families.

Evaluate the spatial arrangement in

cis

-but-

2

-ene and

trans

-but-

2

-ene.

The double bond restricts rotation, placing methyl groups on the same side (

cis

) or opposite sides (

trans

), defining geometric isomerism.

Geometric isomerism is a stereoisomerism type arising from restricted double-bond rotation.

Key Concept

Classification of Structural Isomerism and Stereoisomerism

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