Question

Which one of the following best represents the predicted approximate chemical shift and coupling for the hydrogen(s) indicated with the arrow?1.00 ppm, quartet 2.40 ppm, singlet 2.40 ppm, quartet 3.00 ppm, quartet 2.40 ppm, triplet

Answer 1

Answer:

The answer is quartet 2.40 ppm.

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Explanation:

Solution

Multiplicity or (n+1) rule:

It helps in determination of multiplicity of an individual proton or individual types of proton which are available in the molecule.

Multiplicity =(n+1)

Thus

The non equivalent protons which are attached from adjacent atom is denoted by n.

Now because there are three non-equivalent protons are present at adjacent carbon of methylene group, hence the multiplicity of methylene hydrogen is given as follows:

The multiplicity will be the same for the two hydrogen's. thus we compute multiplicity only for one  hydrogen atom stated below:

Non- equivalent = 3

Multiplicity = (3 +1)

= 4

= Quartet for 2H

A quartet for 2H indicates that the hydrogen atoms attached from the carbon, which is attached one side from a methyl group and the other side form an atom that have no any hydrogens.

Now due +I effect of carbonyl group, chemical shift value is high for these two hydrogens which is exactly at 2.40 ppm or 2.40 Quartet.