Question

ho—ch—o—ch3
ch3
hemiacetal
acetal
neither
ch3—ch2—o—ch—och3
ch3
hemiacetal
acetal
neither

Explanation:

A hemiacetal has the general structure R - CH(OH) - OR', where there is one hydroxyl (-OH) and one alkoxy (-OR') group attached to the same carbon atom. An acetal has the general structure R - C(OR')₂, with two alkoxy groups attached to the same carbon atom. For the first compound HO - CH(CH₃) - O - CH₃, it has a hydroxyl and an alkoxy group on the same carbon, so it's a hemiacetal. For the second compound CH₃ - CH₂ - O - CH(CH₃) - OCH₃, it has two alkoxy groups on the same carbon, so it's an acetal.

Answer:

1. hemiacetal
2. acetal