If two halogen atoms are present in a given compound, reactions with
reducing metals may take different paths depending on how close the
carbon-halogen bonds are to each other. If they are separated by four
or more carbons, as in the first example below, a bis-organometallic
compound may be formed. However, if the halogens are bonded to
adjacent (vicinal) carbons, an elimination takes place with formation
of a double bond.
He does however not provide any explanation for this behavior. It could be that this result is largely empirically based, about some aspects of the Gringard reaction mechanism there is not much known about (or consensus among chemists). I looked at Clayden et al. and Vollhardt & Shore and neither give a satisfying answer. If I find any in an other perhaps more advanced textbook, I'll edit this answer.
If two halogen atoms are present in a given compound, reactions with reducing metals may take different paths depending on how close the carbon-halogen bonds are to each other. If they are separated by four or more carbons, as in the first example below, a bis-organometallic compound may be formed. However, if the halogens are bonded to adjacent (vicinal) carbons, an elimination takes place with formation of a double bond.
He does however not provide any explanation for this behavior. It could be that this result is largely empirically based, about some aspects of the Gringard reaction mechanism there is not much known about (or consensus among chemists). I looked at Clayden et al. and Vollhardt & Shore and neither give a satisfying answer. If I find any in an other perhaps more advanced textbook, I'll edit this answer.
Taken from the Virtual Textbook of Organic Chemistry, which is maintained by William Reusch.
He does however not provide any explanation for this behavior. It could be that this result is largely empirically based, about some aspects of the Gringard reaction mechanism there is not much known about (or consensus among chemists). I looked at Clayden et al. and Vollhardt & Shore and neither give a satisfying answer. If I find any in an other perhaps more advanced textbook, I'll edit this answer.
Taken from the Virtual Textbook of Organic Chemistry, which is maintained by William Reusch.
He does however not provide any explanation for this behavior. It could be that this result is largely empirically based, about some aspects of the Gringard reaction mechanism there is not much known about (or consensus among chemists). I looked at Clayden et al. and Vollhardt & Shore and neither give a satisfying answer. If I find any in an other perhaps more advanced textbook, I'll edit this answer.
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