alkenes

Question 1

what is a hydrocarbon?

Answer 1

Compound containing carbon and hydrogen only

Question 2

What is saturated?

Answer 2

only has single bonds

Question 3

what is unsaturated?

Answer 3

Contains carbon-to-carbon multiple bonds.

Question 4

What is a homologous series?

Answer 4

a family of compounds with same general formula and functional group but each successive member differs by CH2

Question 5

Functional group

Answer 5

Atom or groups of atoms responsible for molecules chemical properties.

Question 6

How are pi bonds formed?

Answer 6

Formed by sideways overlap of two P orbitals, one from each carbon atom of double bond.

Question 7

what is the shape around double bond?

Answer 7

• Three regions of electron density around each carbon atom.
• Three regions repel each other as far as possible so the bond angle around each carbon atom is 120 degrees.

Question 8

what does E/Z isomerism involve?

Answer 8

• A c=c bond.
• Different groups attached to each carbon of the double bond.

Question 9

What is stereoisomers?

Answer 9

• Have same structural formula but a different arrangement of atoms in space.

Question 10

reaction of alkenes with hydrogen.
- change in functional group
- conditions
- type of reaction

Answer 10

alkene -> alkane
condition -> nickel catalyst
type of reaction -> addition/reduction

Question 11

reaction of alkenes with bromine/chlorine
-change in functional group
- conditions
- reagent
- type of bond fission

Answer 11

alkene -> dihalogenoalkane
conditions - room temp
reaction - electrophilic addition
bond fission - heterolyctic
reagent - electrophile

Question 12

what is an electrophile?

Answer 12

an electron pair acceptor

Question 13

reaction of hydrogen bromide/ hydrogen chloride with alkanes
- change in functional group
- mechanism
- conditions
- reagent
- type of bond fission

Answer 13

alkene -> halogenoalkane
condition -> room temp
mechanism -> electrophilic addition
reagent -> electrophile
type of bond fission -> heterolyctic

Question 14

reaction of alkenes to form alcohols
reagent
conditions

Answer 14

reagent - steam
conditions - high temperature 300 to 600 degrees Celsius
high pressure 70 atm
catalyst of concentrated phosphoric acid

Question 15

How to test for alkenes?

Answer 15

• Test for unsaturation.
• Bromine water will change from orange to colourless once shaking.

Question 16

What is markownikovs rule?

Answer 16

H always add on to the side that has the most hydrogen, as this forms the most stable carbocation intermediate.

Question 17

What the most stable alkene and least stable alkene?

Answer 17

most stable - primary alkene
least stable - tertiary alkene

Question 18

Reactivity of alkenes.

Answer 18

Much more reactive than alkanes because the presence of the pi-bond.
- Being on the outside of the double bond, the pi- electrons are more exposed than the electrons in the sigma-bond.
- A pi bond readily breaks and alkenes undergo addition reactions relatively easily.