Homework Answers
1)Ha Proton(pink):
It will be most downfield peak after aromatic protons as it is a 30, benzylic, and has direct –ve inductive effect of –NH2 group. The C atom bearing this proton is stereogenic center. Chemical shift for this proton is 4.1 ppm. Splitting pattern for this proton is doublets of doublet (dd) (Its explanation given in point-2).
Splitting pattern for this proton with chemical shift in Hz are as follows,
ν1 = 235.2 Hz
ν2 = 241.2 Hz
ν3 = 245.4 Hz
ν4 = 250.8 Hz
ν2 - ν1 = 6Hz and ν4- ν3 = 5.4 Hz
i.e. coupling constant J = 5.8 H as average.
2)Hb(green) and Hc (Blue) :
These are diastereotopic protons i.e. replacement of any of these two protons by completely different group or atom will generate stereogenic center at C bearing them and this will lead to the formation of diastereomers hence they are termed as diastereotopic protons.
Diastereotopic protons have different chemical shifts i.e. they are chemically non-equivalent and hence they behave differently with Ha proton. This is reflected in there splitting pattern. Chemical shifts in Hz for these protons are as,
ν1 =148.5
ν2 = 155.5
ν3 =161.7
ν4 =166.2
ν5 = 168.7
ν6 = 171.6
ν7= 179.4
ν8 = 184.8
ν3 - ν1 =6.2 Hz (Vicinal coupling 1,3 coupling).
ν4- ν2 = 10.7 H(Geminal coupling).
ν8 - ν7 = 5.4 Hz.
Such a 3 kinds of coupling indicates doublets of doublets of triplet (ddt) some peaks with accidental overlap.
Hence the ABX pattern for given molecule.
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