91Ó°ÊÓ

The conversion of carbonyl compounds to enol in the presence of either a basic or acidic catalyst is known as enolization.

Butan-2-one is treated with a strong base to undergo enolization. The enol reacts with methyl iodide so that the electrophilic methyl group attacks the carbonyl carbon to form the product.

Given data:

Mass/charge ratio =86

IR absorption= >1500 cm^-1

¹H -NMR spectra = 1.1 ppm (doublet), 2.1 ppm (singlet), 2.6 ppm

(septet)

The molecular formula of the compound is evaluated from the value of mass/charge ratio.

Number of carbon atoms =$\frac{86}{12}$

= 7 Remainder 2

This gives seven carbon atoms and two hydrogen atoms.

Replacing one carbon with (7+2) hydrogen atoms and CH with an O atom gives the molecular formula C₅H₁₀O .

The degree of unsaturation (IHD)$=\frac{\left(\right(2n+2)-x)}{2}$$=\frac{\left(\right(2n+2)-x)}{2}$

where

n= number of carbon atoms

x= (Number of hydrogen atoms) + (Number of halogen atoms) - (Number of nitrogen atoms)

On substituting the values,

the degree of unsaturation (IHD) $=\frac{\left(\right(2×5+2)-10)}{2}$

=1

The value of IHD suggests the presence of a pi-bond.

From the NMR spectra,

1. the doublet at 1.1 ppm attributes to the 6H atoms due to the split of an H;
2. the septet at 2.6 ppm attributes to 1H due to the split of 6H;
3. the singlet at 2.1 ppm attributes to 3H due to the split of 1H; and
4. the IR absorption at >1500 corresponds to the carbonyl stretching.

The required structure of Q is as follows:

Molecular structure of Q