First 3 lectures

Question 1

What is diamagnetic anisotropy?

Answer 1

Different electronic properties in different directions

Question 2

Diamagnetic anisotropy on benzene rings

Answer 2

π cloud - partial negative above and below
σ bonds - overlap of sp2 hybridised orbitals - partial positive charge along the equator

Question 3

Ionic bonds and water

Answer 3

Strength of ionic bonds is significantly reduced in the presence of water due to a shell of water reducing the attraction

Question 4

Why is it easier to break π bonds than σ bonds?

Answer 4

Electrons in π bond are further from the nuclei

Question 5

What is the interaction between aromatic rings known as?

Answer 5

π-stacking interactions

Question 6

Hybridisation of carbon with 2 single bonds and 1 double bond

Answer 6

sp2

Question 7

Conformation

Answer 7

Spatial arrangement of atoms that can be interchanged by single bonds

Question 8

Configuration

Answer 8

Arrangement of atoms in space that distinguishes between stereoisomers

Question 9

How can configurations be interconverted?

Answer 9

By breaking covalent bonds

Question 10

Why does torsional strain occur?

Answer 10

Presence of eclipsed bonds

Question 11

Why does Van der Waals strain occur?

Answer 11

Due to steric strain from atoms being too close together

Question 12

Why does angle strain occur?

Answer 12

Due to distortion of bond angles from typical values in ring systems

Question 13

What is the equation for C-C bond angle?

Answer 13

180x(n-2)/n

Question 14

How can stability of cyclic saturated hydrocarbons be judged?

Answer 14

Using enthalpy of combustion per CH2 unit - lowest is most stable

Question 15

Easson and Steadman’s 3 points of interaction

Answer 15

Each group has a specific binding site and so rotation or interconversion will mean these do not match up

Question 16

Why do racemic mixtures have toxic properties?

Answer 16

Due to the dissociative effect

Question 17

What are π stacking interactions responsible for?

Answer 17

Specific folding patterns of proteins and results in the lipophilic side chain in the inside of the fold compared to the hydrophilic outside

Question 18

What is the equation for the substituent hydrophobicity constant?

Answer 18

πx = LogPx - LogPh
Where Px = molecule with substituent x
Ph = molecule without substituent x

Question 19

What does it mean if substituent hydrophobicity constant is negative?

Answer 19

The substituent is less hydrophobic than H and so increases hydrophilicity of the molecule

Question 20

What does it mean if substituent hydrophobicity constant is positive?

Answer 20

The substituent increases the lipophilicity of the drug

Question 21

What groups have a positive inductive effect?

Answer 21

Alkyl chains

Question 22

Why do EWGs give negative inductive effect?

Answer 22

They decrease electron density on the ring

Question 23

Why does the mesomeric effect occur?

Answer 23

Due to polarisation of the electrons that constitute π bonds

Question 24

What groups give a postitive mesomeric effect?

Answer 24

Electron donating groups due to the lone pair of electrons, which can be donated and stabilise the molecule

Question 25

What does the Hammett substituent constant quantify?

Answer 25

EDG and EWG properties

Question 26

Why does Hammett substituent constant not assess ortho- effects?

Answer 26

Due to steric hinderance

Question 27

What is the equation for Hammett substituent constant?

Answer 27

σ = log (Kx/KH)

Question 28

What does +σ represent?

Answer 28

EWG

Question 29

What does -σ represent?

Answer 29

EDG

Question 30

What is the predominant effect in para?

Answer 30

Resonance

Question 31

What does σ value depend on?

Answer 31

Para and meta positioning

Question 32

Name of amine with 2 R groups and 1 H?

Answer 32

Secondary Amine

Question 33

Which amine is most reactive?

Answer 33

Secondary amines

Question 34

Why do amines have a bond angle of 107°?

Answer 34

Due to lone pair

Question 35

Keq equation for sp3 hybridised N?

Answer 35

Keq = Ka reactant acid/Ka product acid

Question 36

What is indicated if Keq>>0?

Answer 36

Reaction favours products

Question 37

What effect does more hydrocarbons on sp3 hybridized N have?

Answer 37

Lowers aqueous solubility

Question 38

Why are tertiary amines less reactive than secondary amines?

Answer 38

Due to steric hinderance

Question 39

What effect do EDGs have on the basicity of aniline?

Answer 39

Increase the basicity by increasing electron density on the ring

Question 40

Why is aniline less basic than piperidine?

Answer 40

Aniline has N's lone pair delocalised around the ring and therefore less able to bond

Question 41

N's lone pair on pyrrole?

Answer 41

In the π cloud so unable to bond

Question 42

N's lone pair on Pyridine?

Answer 42

Lone pair available for bonding

Question 43

What is guanidine?

Answer 43

N rich functional group which is part of L-arginine amino acid

Question 44

Why is Guanidine a strong base?

Answer 44

Due to resonance delocalisation of the positive charge present on its conjugate acid

Question 45

What are quaternary salts chosen based on?

Answer 45

Solubility pH of resulting solution Strenght of ionic coupling Ease of formation

Question 46

Why is O less likely to be pronated than N?

Answer 46

O is more electronegative than N and therefore is less likely to share its electrons than N

Question 47

Is protonation of sp3 or sp2 O easier?

Answer 47

sp3 as protonated ketone has a lower pKa

Question 48

How do electrons occupy molecular orbitals?

Answer 48

In order of increasing energetic content

Question 49

How can atomic orbitals be more easily combined?

Answer 49

If they have similar shape and energy

Question 50

What is the equations for Bond Order?

Answer 50

Bond order = no. of bonding MOs - no. of anti-bonding MOs / 2

Question 51

What are LUMO and HOMO?

Answer 51

Lowest occupied molecular orbital and Highest unoccupied molecular orbital

Question 52

Why does O not always follow Hund's rule?

Answer 52

Due to its energetic content

Question 53

What orbitals are the electrons in in ground state singlet oxygen?

Answer 53

2 electrons in the same MO - 1 with up spin and 1 with down spin

Question 54

What orbitals are the electrons in in excited state singlet oxygen?

Answer 54

Electrons are in seperate MOs but 1 with up spin and 1 with down spin

Question 55

Multiplicity of energy levels equation

Answer 55

M = 2S + 1

Question 56

Why is 02 2- not a radical?

Answer 56

All HOMO electrons are paired

Question 57

What explains the paramagnetic behaviour of molecular oxygen?

Answer 57

MO theory predicts that oxygen is diradical

Question 58

What is an alcohol with 2 OH groups known as?

Answer 58

Diols

Question 59

Why are phenols stronger acids than alcohols?

Answer 59

Due to delocalisation of negative charge on the conjugate base

Question 60

What do phenoxy radicals tend to do?

Answer 60

Tend to dimerise and end the radical chain reaction

Question 61

How do ethers form explosive peroxides?

Answer 61

In the presence of molecular O and UV light

Question 62

Why are epoxides highly reactive?

Answer 62

Due to torsional strain

Question 63

Why are carboxylic acids acidic?

Answer 63

Due to resonance delocalisation of the negative charge of the carboxylate anion

Question 64

Why are thiols more acidic than alcohols?

Answer 64

Due to its larger size and therfore better at delocalising charge