To arrive at the molecular formula and at the structural formula the different steps involved are
(a) Qualitative analysis, (b) Quantitative analysis
In the qualitative analysis the different steps involved are
(a) Extra element detection
(b) Functional group analysis
In the quantitative analysis the percentage of every element is determined and then the emperical and molecular formulae are determined. Both these are followed by structural elucidation.
The number of `-OH` groups in a compound not containing any other functional group can be determined by

Options

A. `CH_(3)COCl`
B. `CH_()MgBr`
C. `CH_(3)OCH_(3)`
D. Both (a) and (b)

Answer

D

Explanation

The number of `-OH` groups in compound can be esitmated by subtracting the molecular mass of reactant from the molecular mas of product and dividing by 42.
Or by estimating the volule of `CH_(4)` liberated after heating the compound with excess of `CH_(3)MgBr`. If one mole of organic compound gives one mole of `CH_(4)` then it contains one `OH` group. If one mole of organic compound gives `n` moles of `CH_(4)` then there ae `nOH` groups. The Grignard method and `CH_(3)COCl` method can be used only if `-OH` groups is present in the compound. Hence (d) is correct while (c) is wrong.