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PL2002 > First 3 lectures > Flashcards

First 3 lectures Flashcards

1
Q

What is diamagnetic anisotropy?

A

Different electronic properties in different directions

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2
Q

Diamagnetic anisotropy on benzene rings

A

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

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3
Q

Ionic bonds and water

A

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

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4
Q

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

A

Electrons in π bond are further from the nuclei

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5
Q

What is the interaction between aromatic rings known as?

A

π-stacking interactions

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6
Q

Hybridisation of carbon with 2 single bonds and 1 double bond

A

sp2

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7
Q

Conformation

A

Spatial arrangement of atoms that can be interchanged by single bonds

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8
Q

Configuration

A

Arrangement of atoms in space that distinguishes between stereoisomers

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9
Q

How can configurations be interconverted?

A

By breaking covalent bonds

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10
Q

Why does torsional strain occur?

A

Presence of eclipsed bonds

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11
Q

Why does Van der Waals strain occur?

A

Due to steric strain from atoms being too close together

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12
Q

Why does angle strain occur?

A

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

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13
Q

What is the equation for C-C bond angle?

A

180x(n-2)/n

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14
Q

How can stability of cyclic saturated hydrocarbons be judged?

A

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

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15
Q

Easson and Steadman’s 3 points of interaction

A

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

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16
Q

Why do racemic mixtures have toxic properties?

A

Due to the dissociative effect

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17
Q

What are π stacking interactions responsible for?

A

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

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18
Q

What is the equation for the substituent hydrophobicity constant?

A

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

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19
Q

What does it mean if substituent hydrophobicity constant is negative?

A

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

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20
Q

What does it mean if substituent hydrophobicity constant is positive?

A

The substituent increases the lipophilicity of the drug

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21
Q

What groups have a positive inductive effect?

A

Alkyl chains

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22
Q

Why do EWGs give negative inductive effect?

A

They decrease electron density on the ring

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23
Q

Why does the mesomeric effect occur?

A

Due to polarisation of the electrons that constitute π bonds

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24
Q

What groups give a postitive mesomeric effect?

A

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

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25
Q

What does the Hammett substituent constant quantify?

A

EDG and EWG properties

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26
Q

Why does Hammett substituent constant not assess ortho- effects?

A

Due to steric hinderance

27
Q

What is the equation for Hammett substituent constant?

A

σ = log (Kx/KH)

28
Q

What does +σ represent?

A

EWG

29
Q

What does -σ represent?

A

EDG

30
Q

What is the predominant effect in para?

A

Resonance

31
Q

What does σ value depend on?

A

Para and meta positioning

32
Q

Name of amine with 2 R groups and 1 H?

A

Secondary Amine

33
Q

Which amine is most reactive?

A

Secondary amines

34
Q

Why do amines have a bond angle of 107°?

A

Due to lone pair

35
Q

Keq equation for sp3 hybridised N?

A

Keq = Ka reactant acid/Ka product acid

36
Q

What is indicated if Keq»0?

A

Reaction favours products

37
Q

What effect does more hydrocarbons on sp3 hybridized N have?

A

Lowers aqueous solubility

38
Q

Why are tertiary amines less reactive than secondary amines?

A

Due to steric hinderance

39
Q

What effect do EDGs have on the basicity of aniline?

A

Increase the basicity by increasing electron density on the ring

40
Q

Why is aniline less basic than piperidine?

A

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

41
Q

N’s lone pair on pyrrole?

A

In the π cloud so unable to bond

42
Q

N’s lone pair on Pyridine?

A

Lone pair available for bonding

43
Q

What is guanidine?

A

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

44
Q

Why is Guanidine a strong base?

A

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

45
Q

What are quaternary salts chosen based on?

A

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

46
Q

Why is O less likely to be pronated than N?

A

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

47
Q

Is protonation of sp3 or sp2 O easier?

A

sp3 as protonated ketone has a lower pKa

48
Q

How do electrons occupy molecular orbitals?

A

In order of increasing energetic content

49
Q

How can atomic orbitals be more easily combined?

A

If they have similar shape and energy

50
Q

What is the equations for Bond Order?

A

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

51
Q

What are LUMO and HOMO?

A

Lowest occupied molecular orbital and Highest unoccupied molecular orbital

52
Q

Why does O not always follow Hund’s rule?

A

Due to its energetic content

53
Q

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

A

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

54
Q

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

A

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

55
Q

Multiplicity of energy levels equation

A

M = 2S + 1

56
Q

Why is 02 2- not a radical?

A

All HOMO electrons are paired

57
Q

What explains the paramagnetic behaviour of molecular oxygen?

A

MO theory predicts that oxygen is diradical

58
Q

What is an alcohol with 2 OH groups known as?

A

Diols

59
Q

Why are phenols stronger acids than alcohols?

A

Due to delocalisation of negative charge on the conjugate base

60
Q

What do phenoxy radicals tend to do?

A

Tend to dimerise and end the radical chain reaction

61
Q

How do ethers form explosive peroxides?

A

In the presence of molecular O and UV light

62
Q

Why are epoxides highly reactive?

A

Due to torsional strain

63
Q

Why are carboxylic acids acidic?

A

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

64
Q

Why are thiols more acidic than alcohols?

A

Due to its larger size and therfore better at delocalising charge

PL2002 (7 decks)

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