2007-05-23 04:48:58 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
You have to use the rule of multiplicity (n + 1, where n = the number of adjacent protons). If you look at the structure of propanoic acid it has no adjacent protons so then n = 0 so 0 + 1 = 1. That is why the signal in the NMR of propanoic acid's OH group is a singlet. N-propanol has 2 adjacent protons so n = 2 and 2 + 1 = 3. That is why n-propanol's OH group appears as a triplet in the NMR.
2007-05-23 05:00:09 · answer #1 · answered by Anonymous · 2⤊ 0⤋
are you referring to peaks on a proton NMR? Because if so, it is not the OH that is showing the different numbers of peaks. An -OH group will always appear as a singlet, because hydrogens on highly electroneg. atoms (O,N) will always give singlets, that is, their protons don't couple. The different peaks in propanoic acid and propanol are due to the other protons in the molecule.
2007-05-23 11:59:52 · answer #2 · answered by Anonymous · 2⤊ 0⤋
Because in propanol the OH is adjacent to a methylene group:
CH2-OH so it is split into a triplet
in the carboxylic acid the OH in adjacent to cabonyl group - so it's just shifted down field
C(=O)-OH - singlet - downfield
2007-05-23 12:00:56 · answer #3 · answered by Dr Dave P 7 · 0⤊ 0⤋
Due to the different nature of the groups attached.
2007-05-23 12:00:17 · answer #4 · answered by ag_iitkgp 7 · 0⤊ 0⤋