Nmr Spec

Question 1

What is nmr used for

Answer 1

Used to determine the structures of unknown organic substances

Question 2

Why is nmr so good

Answer 2

Easy to obtain a sample
Only small amount of sample needed
It is non destructive

Question 3

Why is c13 used

Answer 3

Has spin and is significant enough to obtain a spectrum

Question 4

Things you need to be able to interpret from a c13 spectrum

Answer 4

Number of peaks tells you number of carbon environments
Location of peaks tells you about the type of carbon environments

Question 5

What does symmetry show

Answer 5

Same environments

Question 6

Tms

Answer 6

Tetra methyl silane
Used as a reference standard for chemical shifts

Question 7

Why is tms used as a standard

Answer 7

Generates 1 sharp peak (as all c are equivalent)
Unreactive so won’t affect sample being dissolved

Question 8

What u need to be able to infer from h nmr spectrum

Answer 8

Number of peaks tells u number of environments
Location of peaks shows u type of proton environment
Area under each peak tells u number of protons in each environment
Splitting shows number of protons in neighbouring carbon

Question 9

Spin rule

Answer 9

N+1
N is number of hydrogens on neighbouring carbon

Question 10

What does o- h always split to

Answer 10

Singlet

Question 11

Solvents

Answer 11

Has to be hydrogen free environment so doesn’t produce any peaks
So solvents using deuterium are used

Question 12

For polar samples

Answer 12

Deuterated trichloromethane - CDCl3

Question 13

Non polar samples

Answer 13

Deuterated benzene
C6D6