Organic: Alkenes

Question 1

how do you describe alkenes

Answer 1

They are unsaturated hydrocarbons, containing a double covalent carbon
The general formula is CnH2n
when cyclic CnHcn-2
high electron density so good nucleophiles
They react by adding across the double bond to form saturated compounds,
starts with ethene

Question 2

describe the bonding within an alkene

Answer 2

sigma covalent bond- electrons between the two c atoms
pi covalent bond-electrons above and below the plane of 6 central atoms, this causes restricted rotation

Question 3

there are many isomers of alkenes
give definition for structural isomers and geometrical isomers

Answer 3

structural- molecules with the same molecular formula but different structural formula -position - chain - functional group
Geometrical- E/Z isomers

Question 4

explain the priority rules for E/Z isomers

Answer 4

look at the atomic numbers on both ends of c=c
highest values opposite= E
highest values together = Z

Question 5

define electrophile

Answer 5

species that is positively charged, accepting an electron pair

Question 6

explain the test for alkenes

Answer 6

bromine water which is orange is added to the sample. if the compound is unsaturated (alkene), an addition reaction will take place and the coloured solution will decolourise, forming dibromoalkane

Question 7

explains Markownikoffs additions finding

Answer 7

The more alkyl groups on the carbocations the more stability so forms more of it, due to electrons push effect lead to more stability and easier form
order of stability of carbocations: tertiary>secondary>primary
so they are more likely to lead to teirtiery substituted products over secondary over primary. remember to answer with comparisions

Question 8

explain what addition polymerisation is

Answer 8

Addition polymerisation is the reaction in which many monomers containing at least one C=C double bond form long chains of polymers as the only product.
he π-bond in each C-C bond breaks and then the monomers link together to form new C-C single bonds

Question 9

why are the polymers non boidegradable

Answer 9

polyalkenes are made of strong non polar c-c and c-h bonds making them very unreactives so they are not affected by enzymes

Question 10

remember

Answer 10

practise reactions for alkenes