Question

Convert each cyclic monosaccharide into its acyclic form.

(a.)

(b.)

(c.)

(d.)

Short answer

Answer

(a.)

(b.)

(c.)

(d.)

Step-by-step solution

Cyclic Monosaccharides

Cyclic monosaccharides are ring-shaped molecules with 5 or 6 carbon atoms or contain five carbons and one oxygen atom. These are converted into acyclic monosaccharides by drawing their Fischer projection.

Conversion of cyclic monosaccharides into acyclic form in a and b

a.) In the first step, place the CHO group on C1 and ${\mathrm{CH}}_2\mathrm{OH}$on C6. As ${\mathrm{CH}}_2\mathrm{OH}$is in the upward direction, it is D sugar, and we know D-sugar has an OH group on the right side at C5. Place the ‘up’ groups on the left and ‘down’ groups on the right.

Cyclic monosaccharide a. into acyclic form

b.) In the first step, place the CHO group on C1 and ${\mathrm{CH}}_2\mathrm{OH}$on C6. As is in the downward direction, so it is L sugar, and we know L-sugar has an OH group on the left side at C5. Now, place the ‘up’ groups on the left and ‘down’ groups on the right.

Cyclic monosaccharide b. into acyclic form

Conversion of cyclic monosaccharides into acyclic form in C

C.) First, convert chair form into cyclic form and then draw its Fischer projection. In the first step, place the CHO group on C1 and ${\mathrm{CH}}_2\mathrm{OH}$on C6. As is in the up direction, and so it is D sugar. D-sugar has an OH group on the right side at C5.

Now, place the ‘up’ groups on the left and ‘down’ groups on the right.

Cyclic monosaccharide c. into acyclic form

Conversion of cyclic monosaccharides into acyclic form in d

D.) In fructose, ${\mathrm{CH}}_2\mathrm{OH}$is in the up direction, so it is D sugar. D-sugar has an OH group on the right side at C5.

Cyclic monosaccharide d. into acyclic form