Alkenes Flashcards
What is an alkene
A hydrocarbon that is unsaturated ( has one or more double bond )
What are the two types of bond
Sigma and Pi
what is a sigma bond
The overlap of two s orbitals
What is a pi bond
The sideways overlap of P orbitals
What is stronger a sigma or pi bond
Sigma
Why are alkenes more reactive than alkanes
Alkanes only have a sigma bond whereas alkenes have pi bonds which are much weaker and therefore easier to break
The double bond has a high e- density and therefore it is more likely to be attacked by nucleophiles
Can double bonds rotate
absaloutly not
what his sterioisomerism
Compounds with the same structural formula but a different arrangement in space
What is z isomerism
When. the dominant groups are on Z- same ziddeee
What is E isomerism
When the dominant group are on different sides
How do you decide priority for Z/E isomerism
go through the groups and find the first difference, the one with the highest Atomic number has priority
What is cis/ trans isomerism
when there are 2 of the same groups around a double bond. Cis means they are on the same side. Trans mean they are on different sides
What is electrophilic addition
When the double bond b and in an alkene opens up and atoms are added to the carbon atom
What is an electrophile
an electron pair acceptor
What are the conditions required to add hydrogen to an alkene
Nickle catalyst 150 degrees
How do you react an alkene with halogens to form dihaloalkanes
The double bonds repel electrons in Br2 making it polar (add delta +/-
Hetrolytic bond fission occurs in Br2 (curly arrow )
The double bond opens up and the delta + Br is added on and a positive carbocation is formed (put a + on the carbon that hasn’t been bonded). Also draw the Br- radical that has formed with 2 delocalised e-
Draw an arrow from the Br radical to the + carbocation and join em
What conditions are needed for steam hydration of alkenes
300 degrees steam and 60-70 atm of pressure
Addition of alkenes with hydrogen halides
Her splits and then its the same
markonikoffs rule
The major product from addition an unsymmetrical compound with an unsymmetrical alkene I the one where the positiver result of bond fission is added to the carbon with the most hydrogens attached
