4. alkenes Flashcards
characteristics of alkenes
- unsaturated hydrocarbons
- high e- density due to double cov bond
[ One sigma and one π bond; the π bonds are exposed and have high e- density]
what mechanism are alkenes susceptible to and why
electrophilic addition because electrophiles attack the -ve charge
electrophiles
electron pair acceptors
they are often delta +ve species, attracted to -ve charges
what molecules can electrophilic addition occur with
conditions
bromine ; room temp no UV
hydrogen bromide ; room temp
sulfuric acid ; conced room temp
process of electrophilic addition
dipoles induced / constant in the molecule
e- pair in C=C donated to delta + , e- pair in cov bond donated to delta -
carbocation formed
nucleophile -ve species attracted to +be charged on C and donates its e- pair
products of electrophilic addition with bromine, hydrogen bromide, sulfuric acid
h alkanes
h alkanes
alkyl hydrogen sulphate. this can be reacted with water to form an alcohol and sulfuric acid again
major product
minor product
product that is more likely to be formed
converse
how is major/minor product determined
carbocation classification
a carbocation is an intermediate stage in the formation of products
the higher the class the increased stability. so the carbocation will remain for longer before reacting. so more chance
it’s more stable because higher inductive effect of a local change in e- distribution to e- donating groups in a molecule
explaining m/m products
the major product is formed via a () carbocation intermediate whereas the minor product is formed via a () carbocation intermediate. () carbocation is more stable than a () carbocation
you could name the major / minor products
addition polymers are formed from
alkenes
they are formed during the reaction of addition polymerisation
poly(alkenes) are unreactive (therefore non biodegradable) because
strong C-C and C-H bonds
non polar bonds, not susceptible to nucleophiles
describe pvc
rigid long close packed polymer chains
why is pvc rigid
uses of pure pvc
strong VDW between polymer chains preventing from moving over eachother
uPVC window frames and guttering
how does a plasticiser change pvc
uses of plasticised pvc
imfs weakened so chains move more easily, so more flexibility
insulation on electrical wires, waterproof clothing
