center was not disturbed, the unknown obviously has the same configuration
as the known. This does not necessarily mean that if the known is (R), the
unknown is also (R). This will be so if the sequence is not disturbed, but not
otherwise. For example, when (R)-1-bromo-2-butanol is reduced to 2-butanol
without disturbing the chiral center, the product is the (S) isomer, even
although the configuration is unchanged, because CH3CH2 ranks lower than
BrCH2, but higher than CH3.
2. Conversion at the chiral center if the mechanism is known. Thus, the SN2
mechanism proceeds with inversion of configuration at an asymmetric carbon
(see p. 426) It was by a series of such transformations that lactic acid was
related to alanine:
center was not disturbed, the unknown obviously has the same configurationas the known. This does not necessarily mean that if the known is (R), theunknown is also (R). This will be so if the sequence is not disturbed, but nototherwise. For example, when (R)-1-bromo-2-butanol is reduced to 2-butanolwithout disturbing the chiral center, the product is the (S) isomer, evenalthough the configuration is unchanged, because CH3CH2 ranks lower thanBrCH2, but higher than CH3.2. Conversion at the chiral center if the mechanism is known. Thus, the SN2mechanism proceeds with inversion of configuration at an asymmetric carbon(see p. 426) It was by a series of such transformations that lactic acid wasrelated to alanine:
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