Electrophilic Addition
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Electrophilic Addition
For an electrophilic addition reaction mechanism of a compound with a double bond and HBr, does the carbon to which the H is added matter?
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Re: Electrophilic Addition
No it doesn't. As long as the hydrogen bonds to a carbon before the bromine atom.
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Re: Electrophilic Addition
Since this is not part of 14B syllabus, I doubt it would make a difference which Carbon you attach the Halide to.
The question usually specifies the product formed, so just follow that.
This is how it works -->
ASYMMETRIC ACROSS DOUBLE BOND - both carbons have different number of hydrogens attached to them.
Electrophilic addition of a halogen acid across an asymmetric double bond is described by
Markovnikov's rule.
The negative part of the addendum goes to the carbon which contains the least number of Hydrogens
Addendum - What you are adding. In this case halogen acid HX (HBr, HF etc)
This means that the halide (X-) attaches to the carbon with the least number of hydrogens.
In addition to this, there is an Anti Markovnikov's rule which states that -
In the presence of a catalyst such as benzoyl peroxide, the negative part of the addendum goes to the carbon which contains the most number of Hydrogens .
This means that the halide (X-) attaches to the carbon with the most number of hydrogens.
This is the general method of looking at an electrophilic addition across a double bond.
Note: both the products are formed (halide on one carbon and the other), the major product however is the one following Markovnikov's rule.
SYMMETRIC ALKENE - both carbons across double bond have same number of hydrogens
The negative part of the addendum goes to that carbon which forms a more stable carbocation.
Different groups have different effect on of stability of carbocation,
thereby affecting the product.
The question usually specifies the product formed, so just follow that.
This is how it works -->
ASYMMETRIC ACROSS DOUBLE BOND - both carbons have different number of hydrogens attached to them.
Electrophilic addition of a halogen acid across an asymmetric double bond is described by
Markovnikov's rule.
The negative part of the addendum goes to the carbon which contains the least number of Hydrogens
Addendum - What you are adding. In this case halogen acid HX (HBr, HF etc)
This means that the halide (X-) attaches to the carbon with the least number of hydrogens.
In addition to this, there is an Anti Markovnikov's rule which states that -
In the presence of a catalyst such as benzoyl peroxide, the negative part of the addendum goes to the carbon which contains the most number of Hydrogens .
This means that the halide (X-) attaches to the carbon with the most number of hydrogens.
This is the general method of looking at an electrophilic addition across a double bond.
Note: both the products are formed (halide on one carbon and the other), the major product however is the one following Markovnikov's rule.
SYMMETRIC ALKENE - both carbons across double bond have same number of hydrogens
The negative part of the addendum goes to that carbon which forms a more stable carbocation.
Different groups have different effect on of stability of carbocation,
thereby affecting the product.
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