Question

What glycosides are formed when each monosaccharide is treated with ${\mathbf{CH}}_{\mathbf{3}}{\mathbf{CH}}_{\mathbf{2}}\mathbf{OH}$, HCl:

(a) $\mathbf{\beta }\mathbf{-}\mathbf{D}\mathbf{-}\mathbf{Mannose}$; (b)$\mathbf{\alpha }\mathbf{-}\mathbf{D}\mathbf{-}\mathbf{glucose}$ ; (c) $\mathbf{\beta }\mathbf{-}\mathbf{D}\mathbf{-}\mathbf{fructose}$ ?

Short answer

Answer

(a.)and

(b.)and

(c.)and

Step-by-step solution

Glycosides

‘Glycosides’ are the acetals in organic chemistry having an alkoxy (OR) group attached to the anomeric carbon (C1). These are assigned by $\mathbf{\alpha }$and$\mathbf{\beta }$ labelsand are generated when a monosaccharide is treated with alcohol and HCl.

Reaction of β-D-mannose and  α-D-glucose with CH3CH2OH and HCl.

a. When $\mathrm{\beta }-\mathrm{D}-\mathrm{mannose}$ is treated with ${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH}$(ethanol) and HCl, it results in the formation of two glycosides shown below:

$\mathrm{\beta }-\mathrm{D}-\mathrm{mannose}$on treatment with ethanol and HCl

b. When $\mathrm{\alpha }-\mathrm{D}-\mathrm{glucose}$ is treated with (ethanol) and HCl, it results in the formation of two glycosides shown below:

$\mathrm{\alpha }-\mathrm{D}-\mathrm{glucose}$on treatment with ethanol and HCl

When β-D-fructose is treated with  CH3CH2OH and HCl.

c. When $\mathrm{\beta }-\mathrm{D}-\mathrm{fructose}$ is treated with${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH}$(ethanol) and HCl, it results in the formation of two glycosides shown below:

$\mathrm{\beta }-\mathrm{D}-\mathrm{fructose}$ on treatment with ethanol and HCl