Question

Calculate absorption spectra lamda(max) of diene , when the parent compound H2C=CH-CH=CH2 contains 3 methyl groups absorbs at 214 nm.

Answer 1

Question #63710, Chemistry / Other

Calculate absorption spectra lamda(max) of diene, when the parent compound H2C=CH-CH=CH2 contains 3 methyl groups absorbs at 214 nm.

Solution:

CONJUGATED DIENE CORRELATIONS:

i) Base value for homoannular diene = 253 nm

ii) Base value for heteroannular diene = 214 nm

iii) Alkyl substituent or Ring residue attached to the parent diene = 5 nm

iv) Double bond extending conjugation = 30 nm

v) Exocyclic double bonds = 5 nm

vi) Polar groups: a) -OAc = 0 nm

b) -OAlkyl = 6 nm

c) -Cl, -Br = 5 nm

Thus:

Alkyl substituent = 3×5 nm = 15 nm

$$\lambda_{\max} = 214 \text{ nm} + 15 \text{ nm} = 229 \text{ nm}$$

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