1.

The specific optical rotations of pure a- and b-D-mannopyranose are + 29.3° and -17.0, respectively. When either form is dissolved in water, specific optical rotation of the equilibrium mixture is found to be + 14.2°. Calculate the percentage of a anomer at equilibrium.

Answer»


Solution :LET FRACTION of a corner=X
`THEREFORE` Fraction of b-anomer =(1-x)
Hence, `x(+29.3^(@)) + (1-x)(-17.0^(@))=+14.2^(@)`
`29.3^(@)x + 17^(@)x = 14.2^(@) + 17^(@)`
x=0.67
`therefore` Fraction of a-anomer = 0.67 or 67%


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