Alkenes

Question 1

What are alkenes and there features

Answer 1

Alkenes are unsaturated HCs because they have more than more covalent bond, so have a high electron density.

Question 2

compare reactivity between sigma and pi?

Answer 2

Pi bonds are weaker because electron density is spread out above and below the nuclei. They have weaker electrostatic attraction so lower bond enthaply.

Sigma has a higher electron density and electrostatic attraction and high bond enthaply due to 2s orbitals overlapping, which has a greater extent than pi

Question 3

In terms of structure why is sigma stronger than pi

Answer 3

Sigma = end on overlaps between s and p on nuclear axis

Pi= sideways overlap two p orbitals perpendicular to nuclear axis

Question 4

Why are alkanes less reactive than alkenes

Answer 4

Alkenes have sigma and Pi bonds, so have a high electron density. Alkanes only contain sigma bonds which are non polar. Pi bonds have a lower bond enthalpy so more reactive.

Question 5

describe location of sigma and pi bond in alkene

Answer 5

Sigma is located around
carbons and pi is in between
H H Hydrogens parallel
C = C
H H