The formula indicates one degree of unsaturation. The low field 1H triplet at δ 9.41 indicates an aldehyde coupled by 2 Hz to two hydrogens at δ 2.16, which is also coupled by 7 Hz. These data account for C₂H₃O (-CH₂CHO) and the one degree of unsaturation. The triplet at δ 0.65 is a methyl group coupled to two hydrogens on an adjacent methylene group. Since this accounts for CH₃CH₂-, all that remains is another CH₂ group. The methylene group attached to the methyl group is coupled to five hydrogens and is therefore the sextuplet at δ 1.10 while the last CH₂ group is the pentuplet at δ 1.34.

You will notice that the coupling constants of the sextet and pentuplet are listed as ~8 Hz. This is because the coupling between the CH₂ at δ 1.34 must be coupled by 7 Hz to δ 2.16 and possibly by 8 Hz to δ 1.10. This subtle difference in the value of J may account for the apparent broadening of the inner peaks of the signals at δ 1.10 and 1.34.

The appearance of five singlets in the ¹³C NMR is in agreement with five different carbons. The signal at 202.0 ppm is in the region for an aldehyde hydrogen. Return to Menu.