alkenes Flashcards
Y12 (strand 1) (33 cards)
what is the general formula for non-cyclic alkenes
CnH2n
what is the general formula for cyclic alkenes
CnH2n-2
what is stronger, the sigma or pi bond
sigma bond
how is the pi bond formed
A P orbital on one carbon overlaps sideways-on with a P orbital on an adjacent carbon atom
what does a sigma bond look like vs a pi bond
sigma bonds are end-to-end
pi bond have a sideways overlap
what type of reactions do alkenes undergo and what happens to the double bond in the reaction
addition reactions
the pi bond breaks but sigma bond remains intact
which atoms are in the same plane in an alkene
the double bond and all atoms directly attached to the Cs involved in it
the double bond contains a concentrated area of __ called __
electrons
an area of high electron density
what happens in addition reactions
the pi bond breaks and new atoms or groups are added onto the molecule to form a single product
why is H+ an electrophile
has no electrons
why is Br-Br an electrophile
can accept e- pair if Br-Br bond breaks
can also have induced dipole
why is H-Br an electrophile
permanent dipole attracted to e-
H+ can accept e- if H-Br bond breaks
why is H2SO4 an electrophile
has a delta + charge so attracted to e-
can accept e- pair if H-O bond breaks
why do alkenes attract electrophiles
they have a carbon-carbon double bond which is rich in electrons (high density)
describe what you would see if you added bromine water to an alkene
bromine water decolourised (brown -> colourless)
what type of species is the intermediate in an alkene electrophilic addition reaction
carbocation
does a molecule formed in an electrophilic addition reaction show EZ isomerism
no because there is no double bond
what is meant by an unsymmetrical alkene
the lengths of the groups / chains attached to the carbons in the double bond are not the same
what is markovnikov’s rule
that the H will join the carbon with the most Hs in it already in an unsymmetrical alkene
how would you properly explain markovnikov’s rule
formed using a (1/2/3*) carbocation which is more stable than (1 down) due to it having more e- releasing alkyl groups
why is a primary carbocation less stable than a secondary one
less e- releasing groups
what are alkyl groups
electron releasing groups, making the charge more negative by counteracting the positive charge on the C
what is the general equation of the reaction between alkenes and conc. sulphuric acid
alkene + sulphuric acid -> alkyl hydrogen sulphate
how is H2SO4 an electrophile
can accept an e- pair if the H-O bond breaks
