Identify correct statements from the following :
A Propanal and propanone are functional isomers.
B. Ethoxyethane and methoxypropane are metamers.
C. But-2-ene shows optical isomerism.
D. But-1-ene and but-2-ene are functional isomers.
E. Pentane and 2, 2-dimethyl propane ai-e chain isomers.
Choose the correct answer from the options given below:

We need to identify the correct statements about types of isomerism.

A. Propanal and propanone are functional isomers.

CORRECT. Propanal ($$CH_3CH_2CHO$$, an aldehyde) and propanone ($$CH_3COCH_3$$, a ketone) have the same molecular formula ($$C_3H_6O$$) but different functional groups. This is functional isomerism.

B. Ethoxyethane and methoxypropane are metamers.

CORRECT. Both are ethers with formula $$C_4H_{10}O$$: ethoxyethane ($$C_2H_5\text{-}O\text{-}C_2H_5$$) and methoxypropane ($$CH_3\text{-}O\text{-}C_3H_7$$). They have the same functional group (ether) but different distribution of alkyl groups around the oxygen. This is metamerism.

C. But-2-ene shows optical isomerism.

INCORRECT. But-2-ene ($$CH_3\text{-}CH=CH\text{-}CH_3$$) shows geometrical (cis-trans) isomerism, not optical isomerism. It has no chiral center.

D. But-1-ene and but-2-ene are functional isomers.

INCORRECT. Both are alkenes (same functional group: C=C double bond). They differ in the position of the double bond, so they are position isomers, not functional isomers.

E. Pentane and 2,2-dimethylpropane are chain isomers.

CORRECT. Both have the molecular formula $$C_5H_{12}$$ but differ in the arrangement of the carbon chain (straight vs. branched). This is chain isomerism.

Correct statements: A, B, and E.

The correct answer is Option (2): A, B and E only.