Alkenes Flashcards
With which type of alkane does an alkene share its general formula?
Cycloalkanes
Are alkenes saturated or unsaturated?
Unsaturated
As the have double C=C bonds
In what type of reaction do alkenes make more bonds?
Addition reactions
Does a double bond in an alkene have high or low electron density?
High electron density
This makes them reactive
What is meant by the term electrophile?
An electron pair acceptor
What makes an alkene an alkene?
It has at least one double C=C covalent bond
What happens in a electrophilic addition reaction?
The double bond in the alkene opens up and atoms are added to the carbon atoms
Why does an electrophilic addition reaction happen?
The double bond has lots of electrons so is easily attacked by electrophiles
The electrophiles lack electrons so are attracted to areas with high electron density
What is the general equation for an electrophilic addition reaction?
CH2CH2 + X-Y ➡️ CH2XCH2Y
All 2s are little!
What happens to X-Y in the 1st stage of an electrophilic addition reaction?
The C=C double bond repels the electrons in X-Y which polarises the X-Y bond crating dipoles
However the molecule could already be polar eg. HBr
What happens in the 2nd stage of an electrophilic addition reaction after the X-Y molecule becomes polarised?
2 electrons from the C=C attack the δ+ X Atom creating a new bond between C1 and the atom. The X-Y bond breaks and the electrons are taken by the Y atom to create a negative ion with a lone pair of electrons. C2 is left with a positive charge when the double bond broke C1 took he electrons from the bond with X and you now have a carbocation intermediate.
What is a carbocation?
An organic ion containing a positively charged carbon atom
What is meant by the word ‘intermediate’ in the term carbocation intermediate?
Intermediate means a short lived, reactive species that forms in the middle of a reaction mechanism
Basically it the carbocation doesn’t last long!
What is the general formula for an alkene?
CnH2n
