Proton NMRProton NMR

All 6 hydrogens are equivalent All 6 hydrogens are equivalent …only make 1-chloropropane…only make 1-chloropropane

These 2 hydrogens are equivalent These 2 hydrogens are equivalent …only make 2-chloropropane…only make 2-chloropropane

- 6 from the methyl groups - 2 from the CH2 group

2 sets of equivalent atoms

Proton NMR Spectrum of EthanolProton NMR Spectrum of Ethanol

Number of peaks = Number

of proton environments

The strength of the absorption is proportional to the number of equivalent H

atoms

H

H

H

H

H

H

Numberof peaks

Ratio of strengthsof absorption signals

1

n/a

1

n/a

2

6:4

Proton NMR spectraProton NMR spectra

Proton NMR spectraProton NMR spectra

Numberof peaks

Ratio of strengthsof absorption signals

2

1:3

4

3:2:2:1

1

n/a

Proton NMR spectraProton NMR spectra

Numberof peaks

Ratio of strengthsof absorption signals

3

6:1:1

2

6:4

1

n/a

Proton NMR spectraProton NMR spectra

Numberof peaks

Ratio of strengthsof absorption signals

3

9:2:1

3

3:2:1

2

3:1

Chemical shift

= 0.7 - 1.6

= 2.0 - 2.9 = 3.3 - 4.3

The chemical shift depends on what other atoms/groups are near the H. The closer the H is to electronegative atoms (e.g. O, Cl), the greater the shift.

For each of the following compounds...For each of the following compounds...

• draw the molecule • predict the number of signals • predict the relative intensity of each signal • predict the approximate chemical shift (δ) of each signal

a) propanoic acid b) 2-chloropropane c) 2-methylpropene d) butanal e) 2-methylbutane f) methyl propanoate