L3 - molecular shape bonding and forces

Question 1

what determines molecule shape and structure

Answer 1

bond lengths
bond angles
bond rotation

Question 2

what determines bond length

Answer 2

atomic radii of atoms (smaller = shorter)

nature of bond (C=C shorter than C-C)

Question 3

why are double bonds shorter than single

Answer 3

due to pull of electrons

Question 4

what is the average distance between 2 bonded atoms

Answer 4

1-2 A

Question 5

what is VSEPR

Answer 5

valence shell electron pair repulsion

electrons will repel as far as they can to have the lowest energy

Question 6

what is hybridization

Answer 6

mixing of orbitals of similar (but different) energy to have lower overall energy

Question 7

can sigma bonds rotate?

can pi bonds rotate?

Answer 7

yes

no

Question 8

put these in order of highest repulsion to lowest repulsion

bond pair & lone pair

Answer 8

lone pair - lone pair
lone pair - bonding pair
bonding pair - bonding pair

Question 9

can the peptide bond rotate and why?

Answer 9

no

it is stabilised by resonance of C=O (delocalised electrons) so has a partial double bond

Question 10

what is unexpected about the peptide bond?

Answer 10

shorter than expected due to partial double bond

Question 11

what does phi represent

peptide bond

Answer 11

rotation angle of N - alpha carbon

Question 12

what does psi represent (peptide bond)

Answer 12

rotation angle of C - alpha carbon

Question 13

what is phi / psi determined by

Answer 13

nature of R group

Question 14

list the types of dipole interactions

Answer 14

1. permanent - permanent
2. permanent - induced
3. fluctuating - induced (london forces)
4. ion dipole - induced dipole

Question 15

what are london forces

Answer 15

fluctuating - induced dipole dipoles

Question 16

can fluctuating dipoles be repulsive?

Answer 16

no

Question 17

compare fluctuating and permanent (/ induced) dipoles

Answer 17

fluctuating occur at much closer distance

Question 18

what factors increase dipole - dipole interactions

Answer 18

1. larger molecule
2. larger SA
3. more e-

Question 19

what causes Hphobic / philic effects?

Answer 19

dipole interactions