Alkenes

Question 1

what are sigma and pi bonds

Answer 1

overlap of s or p orbitals along internuclear axis.

Overlap of p orbitals perpendicular to internuclear axis

Question 2

what is the difference between E and Z isomers

Answer 2

Z: higher priorities on same side of the molecule
E: higher priorities on different sides of molecule

Question 3

reaction of alkenes with hydrogen

Answer 3

alkane product

150C 5-10 atm fine nickel catalyst

Question 4

reaction of alkenes with halogens

Answer 4

dihalo compounds

room temperature and pressure

Question 5

what is the test for an unsaturated hydrocarbon

Answer 5

bromine water goes from orange to colourless

Question 6

reaction of alkenes with hydrogen halides

Answer 6

monohalo compounds
room temp and pressure
hydrogen halide must be freshly generated

Question 7

reaction of alkenes with steam

Answer 7

alcohol product
catalyst: phosphoric acid on support of silica
350C 5-10 atm

Question 8

reaction of alkene with bromine water

Answer 8

2-bromoethanol and hydrogen bromide

room temperature and pressure (shake or bubble gaseous alkene)

Question 9

define electrophile

Answer 9

an electrophile forms a new bond by accepting a pair of electrons from the molecule attacked during the reaction

Question 10

in electrophilic addition, how do the H-Br and Br-Br bonds break.

Answer 10

heterolytic fission, forming :Br-

Question 11

define heterolytic bond fission

Answer 11

the breaking of a covalent bond with both of the bonded electrons going to one of the atoms, forming a cation (+) and an anion (-)

Question 12

what determines the major product in the addition of bromine to an alkene by Hydrogen bromide

Answer 12

the classification of the carbocation.
the most stable is the major product
primary