I'm working on Orgo homework. What I have is an alkyl halide (ClCH2CH2CH2Cl) and Mg. I can't figure out how the Mg creates what I assume will be a Grignard reagent, with carbanions. I need the carbanions to attack a carbonyl on another molecule, but that's not the part I'm having trouble with. So, my question is, how does the Grignard reagent actually form from the Mg + alkyl halide? What are the carbanions formed?
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Mg easily takes on a positive charge so it can bind to electronegative atoms like Cl and Br. In the example you have given, two Cl atoms are present. If you want to develop a successful grignard to attack a carbonyl, you'll have to use only one equiv of Mg to form a complex with only one of the Cl atoms on that molecule.
When the grignard is formed, you assume that the (MgCl) complex on the alkane has a positive charge b/c of the Mg and the remainder of the molecule has a negative charge. This is useful because carbon atoms generally do not have negative charges and this is efficient way to make a carbanion. Once you add a reagent to the grignard with a positive attack location (in your example: the alpha carbon on the carbonyl functional group), the carbanion attached to the MgCl will leave the MgCl to bond to the carbon. The end product is a newly formed carbon-carbon bond, which is extremely useful in organic synthesis.
When the grignard is formed, you assume that the (MgCl) complex on the alkane has a positive charge b/c of the Mg and the remainder of the molecule has a negative charge. This is useful because carbon atoms generally do not have negative charges and this is efficient way to make a carbanion. Once you add a reagent to the grignard with a positive attack location (in your example: the alpha carbon on the carbonyl functional group), the carbanion attached to the MgCl will leave the MgCl to bond to the carbon. The end product is a newly formed carbon-carbon bond, which is extremely useful in organic synthesis.
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single electron transfer (or magic as I call it)