CHEM 2132 | Quiz 1

IR Spectra, Mass Spec

Diagnostic region

1500-4000 cm^-1

clearest info; look here first

-O-H group absorption region

3200-3600 cm^-1

broad

carboxylic acid (-OH group bond)

2200-3600 cm^-1

very broad signal

primary amine (R-N-H₂)

3350-3500 cm^-1

two signals

“vampire” fang

terminal alkynes

~3300 cm^-1

sp² CH

just above 3000

3000-3100; weak

sp³ CH

2850-3000

multiple strong signals

C-H in aldehyde

2750 and 2850

two weak signals

internal alkynes

2100-2200

nitrile

2200-2300

conjugation means the wavenumber will be (higher/lower)

lower

anhydride

1820 and 1760

acid chlorides

1800

ester

1735

aldehyde (carbonyl)

1730

ketone

1720

carboxylic acid

1715

amide

1650

below 3000 cm^-1

sp3 C-H (majority)

slightly above 3000 cm^-1

sp2-CH (double bonds present)

double bond carbonyl range

1650-1820 (STRONG)

C=C double bond

1600-1700 (weak)

degrees of unsaturation formula

(2C + 2 + N - H - X)/2

methyl radical

15 amu

ethyl radical

29 amu

propyl radical

43 amu

butyl radical

57 amu

loss of water (alcohols)

M - 18 amu

alpha cleavage -OH

(M-R)

a terminal alkyne is not present if the range ____ is absent

2100-2200

loss of 28

C2H4, CO, N2

increasing ring strain (increases/decreases) frequency

increases

for O-H bonds, more steric hindrance = less H-bonding = the peak will be (wide/narrow)

narrow

(T/F) higher s character = higher wavenumber

true

C=C stretch from benzenes

1450-1600 cm^-1

Resonance decreases frequency

Higher intensity of signal at a lower energy

conjugation will (increase/decrease) frequency due to more single C-H bond character

decrease