organic chemistry - bonding and structures

Question 1

what is meant by octet rule?

Answer 1

the way in which atoms bond to allow them to achieve the electron configuration of the nearest noble gas - normally 8 electrons

Question 2

what are the characteristics of a sigma bond?

Answer 2

electron density is between the nuclei
symmetrical about the axis
can rotate freely
BE 110Kcal/mol

Question 3

what is the bond dissociation energy of a pi bond?

Answer 3

60kcal/mol

Question 4

what is a double bond made up of?

Answer 4

1x sigma bond, 1x pi bond

Question 5

what is a triple bond made up of?

Answer 5

1x sigma bond, 2x pi bond

Question 6

what is the effect of pi bonding?

Answer 6

pi bonds create a barrier to free rotation, molecules with a lot of pi bonds are much more rigid

Question 7

why are conjugated hydrocarbons more stable?

Answer 7

1. delocalisation of charge through resonance

2. hybridisation energy

Question 8

when is there a charge separation?

Answer 8

if the chemical bond is made up of atoms of different electronegativity

Question 9

what are the four most electronegative elements and what is their electronegativity?

Answer 9

fluorine - 4.0
oxygen - 3.5
nitrogen - 3.0
chlorine - 3.0

Question 10

what is dipole moment?

Answer 10

a measure of the charge separation - the larger the dipole moment, the larger the charge separation

Question 11

when might a molecule not have a dipole?

Answer 11

no charge separation between atoms

molecule is symmetrical