Stereoisomers

Question 1

what are stereoisomers?

Answer 1

compounds with the same structural formula but a different arrangement in space

Question 2

why do some alkenes have stereoisomers?

Answer 2

due to the lack of rotation around the carbon carbon double bond

Question 3

when do you get E and Z isomers?

Answer 3

when the double bonded carbon atoms each have two different atoms or groups attached to them.
E-isomer: two carbon atoms have the ‘highest priority groups’ on opposite sides.
Z-isomer: ‘highest priority groups’ are on the same side.

Question 4

what is cis -trans isomerism?

Answer 4

-the two carbon atoms either side of the double bond have at least one group in common.
cis isomer- two identical groups on the same side of c-c double bond.
trans isomer- two identical groups on opposite sides of the c-c double bond.

Question 5

what happens in an electrophilic addition reaction and why do they occur?

Answer 5

the double bond in an alkene opens up and atoms are added to the carbon atoms
they happen because the double bond has got plenty of electrons and is easily attacked by electrophiles

Question 6

what is an electrophile and nucleophile?

Answer 6

electron pair acceptor
electron piar donator

Question 7

describe what happens in the mechanism of the reaction of but-2-ene and hydrogen bromide.

Answer 7

1. bromine is more electronegative than hydrogen so hydrogen bromide is polar.
2. the electron pair in the pi bond is attracted to the partially positive hydrogen atom causing the bond to break.
   3.a bond forms between the hydrogen atom of the H—Br molecule and a carbon atom that was a part of the double bond.
   4.the H—-Br bond breaks by heterolytic fission, with the electon pair going to the bromine atom.
3. a bromine ion (Br-) and a carbocation are formed. a carbocation contains a positively charged carbon atom.
   6.in the final step, the Br- ion reacts with the carbocation to form the addition product.