chapter 13 Flashcards
what are alkenes?
unsaturated hydocarbons (contain double C=C bond)
what is the general formula for alkenes?
CnH2n
what are Pi bonds caused by?
sideways overlap of P-orbitals above and below the sigma bond
how do you draw before and after of a Pi bond?
two dumbbell shapes on the before
joined together on the after
why are alkenes more reactive?
weaker Pi bond
what is stereoisomerism?
same structural formula
different arrangement of atoms in 3D space
E/Z isomerism only occur in compounds with…?
a C=C double bond
two different groups attached to it
how do you tell between E and Z isomerism?
Z zee zame zide!!!!!
high priority
what is an elimination reaction?
a small molecule is removed from a larger molecule
what are some reactions of alkenes?
hydrogenation
halogenation
addition polymerisation
hydration
what do double bonds in alkenes create?
high electron density region
due to presence of Pi electrons
what does a high density of Pi electrons do?
attracts electrophiles
what are electrophiles?
atom/group of atoms attracted to an electron rich centre and accepts an electron pair
usually positive ion/molecule
what do you do to show the electrophilic addition mechanism first stage?
add charges to small molecule/ion (positive is closest to the double bond and is an electrophile)
curly arrow from double bond to electrophile
curly arrow from single bond to the negative part of the molecule
what do you do to show the electrophilic addition mechanism second stage?
draw carbocation intermediate (contains positively charged carbon)
draw a + next to one carbon
draw a lone pair of electrons on the single molecule and a negative sign
draw a curly arrow from the lone pairs to the positve carbon
what is Markownikoff’s rule?
major products form via the most stable carbocation intermediate
(primary, secondary, tertiary carbocation)
how do carbocations increase stability?
more alkyl groups attached to positive carbon atom the more stable the carbocation
what happens during addition polymerisation?
unsaturated alkenes undergo addition polymerisation to form long saturated polymer chains
what are the risks of polymers?
non-biodegradable due to lack of reactivity
what are the solutions to the risks of polymers?
recycling (stop plastic going to landfills, costly, mixed polymers are useless)
fuel (produce heat, generate steam, power turbines to produce electricity)
what is the difference between biodegradable polymers and photodegradable polymers?
biodegradable broken down by bacteria in water, CO2, biological compounds
photodegradable broken down by absorbing light
what must a compound have to be a cis-trans isomer?
C=C double bond
two different groups attached to each carbon double bond
one of the attached groups on each carbon atom has to be the same
what is trans-isomerism?
trans - across the double bond
what is cis-isomerism?
cis - same side of the double bond
