OChem II Mass Spec

high frequency of vibration =

high energy

strong bonds =

high frequency

high atomic mass =

low frequency

highest frequency =

highest bond strength, lowest mass

IR spec > 3000 cm^-1

unsaturated C-H bonds, sp and sp2 hydridized

IR spec < 3000 cm^-1

saturated C-H bonds, sp3

alcohols appear as a

smooth absobance peak, and have NO carbonyl absorbance ~1760-1670 cm^-1

carboxylic acids appear as

a “jagged peak” due to more interferance and has a carbonyl peak

an NMR singlet

has no “neighbors”

an NMR singlet that integrates at 3 is

usually an isolated methyl group

exchangeable protons frrom solvent

protons directly attached to EN atoms (usually N or O) cause broadened or disappearing peaks with inaccurate integrations

aromatic protons and solvents

cause unexplected NMR splits

C13 Chemical shifts tell us

• how many types of C

• what type of chemical environment

• confirms NMR