CHM 256

parent ion

the m/z signal that matches the mass of the analyte compound

base peak

tallest peak in the spectrum

electron ionization (ei)

bombardment of the analyte with an electron beam to create radical cations to be seen by the detector

15 amu

CH3 radical

unbranched alkane fragmentation

can form a series of cations differing by 14 amu (CH2)

branched alkane fragmentation

occurs to give secondary and tertiary cations

cycloalkane fragmentation

loss of side chains and loss of ethylene from ring

alkene fragmentation

-strong molecular ion peak

-occurs to form allylic cations

alkyne fragmentation

-strong molecular ion peak

-occurs to form propargyl cation

alcohol fragmentation

-molecular ion peak is weak

-most common loss is H2O

what is the principle that allows us to use mass spectrometry to determine molecular weight of a compound?

a beam of higher molecular weight cations is deflected less by a magnetic field

what set of molecular ions does dibromoalkane possess?

three molecular ions in a 1:2:1 ratio, separated by 2 mass units

alkane IR C-H stretch range

3000-2850 cm-1

alkene C-H Sp2 stretch range

3100-3000 cm-1

alkene C-H Sp3 stretch range

2960-2850 cm-1

aromatic C-H stretch range

3150-3050 cm-1

alkyne C-H Sp stretch range

~3300 cm-1

alkyne C☰C stretch range

2250-2100 cm-1

C☰N stretch range

2260-2240 cm-1

alcohol O-H stretch range

3500-3200 cm-1

carboxylic acid O-H stretch range

3400-2400 cm-1

aldehyde C=O stretch range

1740-1720 cm-1

ketone stretch range

1725-1705 cm-1

aldehyde C-H stretch range

~2700 cm-1

carboxylic acid C-O stretch

1300-1000 cm-1

toluene

benzene ring with methyl group

phenol

benzene ring with alcohol group

aniline

benzene ring with NH2 group

benzaldehyde

benzene ring with an aldehyde group

benzoic acid

benzene ring with carboxylic acid

anisole

benzene ring with OCH3

1,2- attachment on benzene

O- / Ortho-

1,3- attachment on benzene

M- / Meta-

1,4- attachment on benzene

P- / Para-

provides a way to weigh molecules

mass spectrometry

chlorine distribution ratio

3:1

bromine distribution ratio

1:1

mass spectrometry can only detect ____

cations

CH3 fragment mass

15

OH fragment mass

17

H2O fragment mass

18

C2H4 fragment mass

28

CO fragment mass

28

C2H5 fragment mass

29

CHO fragment mass

29

CH2OH fragment mass

31

OCH3 fragment mass

31

Cl fragment mass

35

C3H3 fragment mass

39

C3H5 fragment mass

41

C3H7 fragment mass

43

CH3CO fragment mass

43

CH3CHO fragment mass

44

CO2 fragment mass

44

CH3CHOH

45

CH2CH2OH fragment mass

45

CO2H fragment mass

45

C4H9 fragment mass

57

C2H5CO fragment mass

57

xylene

benzene with 1,4 methyl groups