McMurry (Kap. 14,12) - spectroscopy of Aldehydes and Ketones

Question 1

IR absorptions of aldehyde and ketones (page 522 table).

Generally, within which range does the aldehyde and ketone show in the IR spectre?

Answer 1

Within the range of 1660-1770 cm^-1.

Additionally aldehydes show 2 characteristic C-H absorptions in the range 2780 and 2820 cm^-1.

Question 2

H-NMR of aldehydes and ketones (page 523-524)

What range do aldehydes and ketones show in H-NMR and C-NMR?

Answer 2

In H-NMR the aldehyde protons (RCHO) absorb near 10 ppm.

The aldehyde protons show spin-spin coupling with protons from neighboring carbon (atecaldehyde - show quartet at 9,8 ppm - indicating three protons neighboring the aldehyde group).

Hydrogens next to the carbonyl group are usually deshielded and absorb normally at 2-2,3 ppm.

Methyl ketones - show sharp three proton singlet near 2,1 ppm.

The carbonyl carbon atoms of aldehyde and ketone have CNMR at 190-215 ppm. Aromatic and a,B-unsaturated carbonyl carbons ansorb in 190-200 ppm region.

Question 3

Mass spectrometry of aldehydes and ketones page 524-525

Answer 3

Mass spectrometry of aldehydes and ketones page 524-525