Organic Chem-addition Reaction Flashcards
What’s an electrophile??
They are electron pair acceptors with a whole or partial positive charge eg a Br atom in a H—BR bond
Explain step one in electrophilic addition mechanism between ethene and H—Br
The H is less electronegative than the Br and becomes slightly positive (electrophile). The Pi electrons in the double bond are attracted to the Postive Hydrogen, repelling the shared electrons in the H—Br bond. The bond breaks with heterolytic fission (uneven,both electrons go to Br)
What happens at the second stage of the electrophilic addition mechanism of ethene and HBr
The postive H attaches to the carbon on one side of the double bond, and a positive carbocation is left on the other carbon in the bond. A Br- ion is left from the first stage with two electrons.
What happens at the last stage of the electrophilic addition mechanism of ethene and HBr
Negative Br is attracted to the carbocation and attaches to it
What is Markovnikofs rule??
When a H+ ion from an UNSYMMETRICAL molecule is joining another UNSYMMETRICAL molecule, the H+ion will attach to the carbon that has the most hydrogen’s already attached to it. The other element eg Br will attach to the other one.
(Hydrogen goes where there’s already lots of Hydrogen)
How can you use markovnikoffs rule to work out which of two isomers are going to be made more??
Two isomers can be made during electrophilic addition, but the one that follows markovnikoffs rule is going to be made more
Explain primary/secondary/ tertiary carbocations
The most stable carbocation is a tertiary carbocation
Tertiary=3 carbons attached to the carbon with a carbocation on
Secondary= 2 carbons attached to the carbon with a carbocation on
Primary= 1 carbon attached to the carbon with the carbocation on
