NMR Spectroscopy

chemical shifts and multiplicity patterns

methyl protons chemical shift

0.9 ppm

methylene chemical shift

1.2 ppm

methine chemical shift

1.7 ppm

how does resonance affect chemical shifts

partial positive charges on hydrogens increase the chemical shift for its protons

chemcial shift of allylic protons

~2 ppm

chemical shift for alkynyl protons

~2.5

chemical shift for aromatic methyl protons

~2.5 ppm

alkyl halide proton chemical shift

2-4 ppm

vinylic proton (directly part of a pi system)

4.5-6.5

aryl (attached to a benzene ring) proton chemical shift

4.5-6.5

aldehyde proton

~10 ppm

carbonylic acid proton chemical shift

~12 ppm

multiplicity pattern

n+1 peaks

2 doublets (next to each other)

R-CH-CH-R

3 proton triplet signal & 2 proton quartet signal

isolated ethyl group (R-CH2-CH3)

six proton doublet and 1 proton septet

isolated isopropyl group

0-3 hz coupling constant

geminal vinylic protons/terminal alkene

11-18 hz coupling constant

trans protons

5-10 hz coupling constant

cis protons

multiplet between 7 and 8 ppm w/ 5 protons

mono substituted benzene ring w/ only carbon attached

5 proton multiplet at 8 ppm

Ph-CHO

5 proton multiplet w/ 2 peaks between 7-8

mono subsituted benzene with oxygen directly attached

protons bonded to oxygen and nitrogen

appear as broad singlets and do not split there neighbors

how do halogens affect the degree of saturation?

decrease number of hydrogens by one

saturated hydrocarbon

has 2n+2 amount of hydrogen atoms

how does nitrogen affect the degree of saturation

increase the number of hydrogens by 1

T/F oxygen does not affect the number of hydrogens

true

carbon atoms in carbonyl groups (c=n carbons) are highly DE shielded

true

mono subistuted benzene rings have ___ signals in c13 nmr

5

disubstituted benzen rings have ___ signals in c13 nmr

3-4