Question

7. Given the following 'H NMR spectrum for a compound with molecular formula C.H.CI:. . (4x2)+2-(S-2) - 0 - 6 = 4 swaelim a. (4 points) Propose a structure for the compound b. (6 points) Describe each signal in terms of its integration, splitting and chemical shift. c 11 10 9 8 7 6 5 4 pom

Answer 1

Solution -

# Molecular formula of compound = C₄ H ₈Cl₂

We have to calculate index hydrogen deficiency by comparing with saturated hydrocarbon formula,

C_n H _{2 n +2}

here n = 4 , by putting values into above formula, then

C₄ H _(2x4)+2

C₄ H₁₀

now by comparing formula, index hydrogen deficiency = (10)-(8-2)/2

= 0

here '2' is taken for subtraction due to correction for two' Cl ' atom.

a and b)

By observing NMR spectrum, let's see signal position and splitting pattern based on n+1 rule, where n stands for number of adjacent proton to corresponding signal. Signals are labeled as A,   B, C and D.

A) 4.25 ppm (1 H, sextet)

Deshielded due to vicinity of electronegative chlorine atom and splitted as sextet due to vicinity of CH₃ and CH₂ group

B) 3.75 ppm (2H , t)

Deshielded due to vicinity of electronegative chlorine atom and split as triplets due to vicinity of only CH₂ group.

C) 2.0ppm (2H , quartet)

This is CH₂ group of protons and split as quartet due to vicinity of - CH-Cl and CH₂ group.

D) 1.5 ppm (3H, doublet)

This is CH₃ group of protons and split as doublet due to vicinity of only CH-Cl group.

Based on above finding structure of compound would be 1,3-dichlorobutane .

Let's see structure along with label assignment-

Date. P predictad Strture D CH CI 1,2-dichlerobutane