Another D-2-ketohexose, psicose, yields a mixture of allitol and altritol when reduced with ${NaBH}_4$ (see Problem 44). Determine the structure of psicose.

Problem 44:

One of the D-2-ketohexoses (see the previous problem) is called sorbose. On treatment with ${NaBH}_4$, sorbose yields a mixture of gulitol and iditol. What is the structure of D-sorbose? (Gulitol and iditol are the alditols acquired by reduction of gulose and idose.)

Previous problem:

How many D-2-ketohexoses are there? Sketch them.

Look up the structures of maltose and sucrose in the said section, and explain why maltose is reduced by NaBH$_4$ but sucrose is not.

Sketch D-ribulose in its five-membered cyclic $\beta$ hemiacetal form.

Uncoil allose and write it in its open-chain form.

The indicated cyclic structure is that of allose. Is this a furanose or pyranose form? Is it an $\alpha$ or $\beta$ anomer? Is it a D sugar or L sugar?

Assign R or S stereochemistry to each chirality center in ascorbic acid.

The indicated structure is the structure of ascorbic acid (vitamin C). Does ascorbic acid have a D or L configuration?

Make an open-chain structure for a five-carbon amino sugar.

Sketch Fischer projections of both (R)-2-chlorobutane and (S)-2chlorobutane.

Make an open-chain structure for a deoxyaldohexose.

Make an open-chain structures for a ketotetrose and a ketopentose.

Sketch the structures of the products acquired from reaction of cellobiose with the following:

(a) NaBH

(b) ${Br}_2, {H}_2 {O}$

Which of the other six D aldohexoses yield optically active aldaric acids, and which yield optically inactive aldaric acids? (See the previous problem.)

Previous problem:

D-Glucose yields an optically active aldaric acid on treatment with nitric acid, but D-allose yields an optically inactive aldaric acid. Discuss.

D-Glucose yields an optically active aldaric acid on treatment with nitric acid, but D-allose yields an optically inactive aldaric acid. Discuss.