Question

For the chemical structure given below, identify the group of protons that is:

A)most shielded

B)least shielded

C)the most downfield

D)the most upfield

Answer 1

Concepts and reason

In nuclear magnetic resonance spectroscopy, the resonance frequency is observed with the reference to the standard compound (0 ppm), is represented as the chemical shift.

The chemical shift varies according to the molecules present in the structure, and it is measured in ppm.

The upfield and downfield of the atom can be identified with the help of chemical shift values.

Fundamentals

Most shielded:

The protons that are present in electron – rich region is the most shielded region. The most shielded region has less chemical shift.

Least shielded:

The protons that are present near the electron withdrawing group, are represented as the less shielded region. In this region, the chemical shift value is higher.

Upfield:

The chemical shift with lower value, which is nearer to the standard (0 ppm) value, is known as the upfield. It is also represented as the most shielded region.

Downfield:

The chemical shift with higher value, which is located far away from the standard value, is known as the downfield. It is also represented as the most deshielded region.

(A)

(B)

(C)

(D)

Ans: Part A

Part B

Part C

Part D