Addition reaction of alkenes Flashcards
what are alkenes attacked by and why?
electrophiles due to their double bond
Name elecrtophiles
NO2- H+ H-Br (any halogen alkane) H2SO4-
Describe the test for an alkene (or a C=C)
Add bromine water and colour should go from brown- orange to colourless
Why is the sigma bond stronger than pi
this is because of theoverlap at greater extent, the electrons are held more tighly between the two carbons
Sig
End on overlap s
Pi
Sideways p overlap
Decribe halogenation where alkene is attacked by halogen
Bromine is non polar and and is polarised causing electrons to move to more elctronegative creating temporary dipole
An electron pair is attracted to br+ and breaks bond forming carboacation.
Alkane is formed where its colourless dibromo.
Describe hydrogenation where alkene reacts with hydrogen
This is done with nickel catalyst and turns into just an alkane
How is margarine made
vegatable oil is unsatured so has a C=C double bond and when reacte with hydrogen turns to single convering to maragrine
Describe hrydation reaction where alkene reacts with water
Using steam and phosphoric acid catalyst turns it into a alcohol (Alkane with OH group).
Describe halogen halide reactions etc. alkene reacting with H-Br
Electron pair in double bond is attracted to H+ and forms bond which breaks H-Br. Crabocation is formed and Br- is attracted to C+ forming a bromoalkane.
Describe reactions where potassium mangate is used on an alkene
Potassium mangate is an oxidsing agent which makes a diol on the alkane formed. This is two function hydoxyl groups- OH and OH
what is the trend in terms of carbocation stablilty in structure
Teritary structures are the most stable and least for primary because there tend to be more electron releasing alky groups attached to carbon, allowing the more major product to be formed
