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Carbohydrates fall under the category of biomolecules and have a significant role in controlling the function and structure of living cells. Cyclic acetals and hemiacetals are a part of several carbohydrates.

Galactose belongs to the category of aldohexoses. Galactose molecules can be connected with glucose leading to the formation of lactose.

Stereogenic centres in-D-galactose

b. The carbon containing the alkoxy group and the hydroxyl group is referred to as the hemiacetal carbon. The hemiacetal carbon of -D-galactose is represented by an asterisk and can be given as:

Hemiacetal carbon of -D-galactose

c. The position of the OH group is in the equatorial position for -D-galactose. The structure of -D-galactose can be given as:

Structure of -D-galactose

d. A hemiacetal is formed on the cyclization of poly hydroxyl aldehyde. The hydroxyl group on the fifth carbon attacks the aldehyde group leading to the formation of

hemiacetal. The structure of polyhydroxy aldehyde that cyclizes to -D-galactose and -D-galactose can be given as:

Structure of polyhydroxy aldehyde

e. Cyclic hemiacetals are converted to acetals when it is treated with alcohol in the presence of acid. The reaction can be given as:

Treatment of -D-galactose with CH₃OH