chemistry 6.9 - reactions of alkenes

What happens when you add H to C=C bonds?

Alkanes formed

How is margarine made?

Hydrogenating unsaturated vegetable oils as when you remove the double bonds you increase the melting point making it solid at room temperature

What does an alkene + halogen make?

Dihalogenoalkanes

How are double bonds adding in relation to the double bond?

Across it

What do alkenes do when they react with bromine water and why?

They de colourise it because the bromine is remove pd from the water and is added across the double binds to form dibromoalkane

What does alkene + water + catalyst + high temp + high pressure form?

An alcohol

What happens when alkenes react with purple acidifies potassium manganate (VII) and what is produced?

Decolourise it and firm a diol (alcohol with 2 OH groups

What forms when hydrogen halide + alkene react?

Halogenoalkanes

How many possible products are there when a H halide reacts with an unsymmetrical alkene?

2

What is a carbocation?

Highly reactive organic ion with a positively charged C and only has 3 bonds. Formed when a double bond in an alkene breaks due to an electrophile (e.g H+ or partially charged H) leaving one of the Cs with only 3 bonds (2 Cs it could be)

Why are carbocations with more alkyl groups more stable?

They feed electrons to the positive carbon

Are stable or unstable carbocations more likely to form?

Stable (more alkyl groups (CnHx))

What are major and minor products?

Major - more likely to form = the more stable carbocation’s product

Minor- least likely to form = less stable carbocation’s product

What is Markownikoff’s rule?

The major products form hydrogen halide + unsymmetrical alkene is the product where the H adds to the C with the most H already attached to it (e.g left C in C=C could have H and H bonded to it whilst the right H had CH3 (only the C will be bonded to the C in the double bond) and H bonded to it so the major product will be formed in the reaction with the right C being the positively charged one (the secondary carbocation)

What is a primary carbocation?

Where there is only 1 alkyl group bonded to the C, so 2 Hs will be bonded and that will be it as carbocations only have 3 bonds

(Secondary will be 2 alkyl groups and tertiary will be 3 and will be the most stable)