Unit 1 Flashcards
(41 cards)
How do you determine the number of unsaturations from a structure?
Generally, 1 unsaturation per ring per double bond
Formula for # of unsaturations
C -1/2H +1/2N +1 -1/2X
Toluene
Benzene w/ a methyl
Phenol
Benzene w/ an alcohol
Analine
Benzene w/ an amino group
Benzaldehyde
Benzene w/ am aldehyde
Benzoic acid
Benzene w/ a carboxylic acid
Anisole
Benzene w/ OCH3
Benzene as a substituent
Phenyl
How do you know which carbon is C1?
the parent structure gets C1 or the 1st alphabetical substituent
What does M+2 mean in mass spectrometry?
There are isotopes of either Br or Cl
What are the Br isotopes? What ratio do they occur in?
79Br : 81Br
1 : 1 ratio
What are the Cl isotopes? What ratio do they occur in?
35Cl : 37Cl
3 : 1 ratio
List the atomic weights of CHON?
C 12
H 1
O 16
N 14
List the cations in order of most stability?
benzyl ~ alyllic > tertiary > secondary > primary > methyl
How do unbranched alkanes fragment?
They form a series of cations differing by 14 amu. Note: no methyl cation forms.
How do branched alkanes fragment?
Fragmentation occurs to give secondary and tertiary cations.
How do cycloalkenes fragment?
Fragmentation occurs to give a loss of side chains and a loss of ethylene from the ring.
What does a loss of 28 amu mean in mass spec?
There is a cycloalkene that has lost ethylene, breaking up the cyclo part.
How do alkenes fragment?
Will show strong molecular (parent) ion peak.
Alyllic cations will form, NOT vinyl cations.
charge on neighboring carbon, NOT on double bond
How do alkynes fragment?
Will show strong molecular ion peak
Will form propargyl cation (charge on neighboring carbon), NOT on triple bond
How do alcohols fragment?
- loss of H2C=O+H
-loss of H2O, taking H from 3rd carbon away
How do benzene derivatives fragment?
Benzyl cations will form with M=91
How do aldehydes fragment?
- aldehyde cation will break off (-29 amu)
- loss of hydrogen (-1 amu)
