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Organic Chemistry > Fundamentals of Organic Chemistry > Flashcards

Fundamentals of Organic Chemistry Flashcards

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1
Q

energy in stable arrangement?

A

low

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2
Q

gain in energy =

A

unfavourable

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3
Q

loss of energy =

A

favourable

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4
Q

electron affinity

A

energy released after adding an electron

forms anion

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5
Q

ionisation potential

A

energy required to remove an electron

forms cation

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6
Q

why side of periodic table are low IPs?

high EAs?

A

left

right

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7
Q

what is polarity?

A

the tendency of molecules to align when placed in an electric field

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8
Q

why does bond polarity occur?

A

differences in electronegativity

= intrinsic ability of an atom to attract electrons in covalent bond

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9
Q

electronegativity trend

A

higher values as you go right or up

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10
Q

inductive effect

A

shifting of electrons in bond in response to electronegativity of nearby atoms

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11
Q

dipole moment

A

measure of polarity due to separation of charge masses of + / - charges

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12
Q

dipole moment - formula

A

µ = q x r

q = charge
r = distance

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13
Q

dipole moment - units

A

Debye (D)

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14
Q

solubility of polar/non-polar solvents

A

polar = soluble in polar solvents (e.g. water)

non-polar = soluble in non-polar solvents (insoluble in water)

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15
Q

when are atoms likely to be covalent?

A

electronegativities differ by < 2

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16
Q

when are atoms likely to be ionic?

A

electronegativities differ by > 2

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17
Q

relative energy of resonance hybrid compared to Lewis structures

A

lower

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18
Q

when do resonance structures occur?

A

2 or more Lewis structures can be drawn

different arrangement of electrons but identical arrangements of atoms

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19
Q

what does the resonance arrow represent?

A

shift of TWO electrons

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20
Q

mesomeric effect

A

when substituent = EWG

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21
Q

why does a nitro group stabilise negatively charged conjugate bases?

A

strongly EWG -> withdraws electron density to stabilise negative charge

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22
Q

why are carboxylic acids stronger than alcohols?

A

carboxylate anion = resonance stabilised

lone pair on O conjugates with C=O

negative charged shared between TWO atoms

alcohols -> alkoxide O- localised to ONE atom

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23
Q

tautomers

A

rapidly interconverting isomers

different location of H

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24
Q

nucleophiles

A

donate electrons

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25
Q

electrophiles

A

accept electrons

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26
Q

basicity

A

affinity of a reagent towards a PROTON

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27
Q

nucleophilicity

A

affinity of a reagent towards a CARBON / OTHER ATOM

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28
Q

which bond is broken first - σ or π ?

A

π - weaker / more easily polarisable

σ bond is stronger because overlap is better head on compared to sideways

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29
Q

direction of movement in organic mechanisms?

A

nucleophile -> electrophile

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30
Q

nucleophilic vs electrophilic

A

[nucleophilic]

δ - / -
HOMO
reacts with δ + / +

[electrophilic]

δ + / +
LUMO
reacts with δ- / -

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31
Q

nucleophilic sites

A
  1. heteroatom with l.p.
  2. multi-carbon bond
  3. δ- C - Z δ+
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32
Q

electrophilic sites

A

δ+ C - X δ-

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33
Q

nucleophilic strength - factors

A

[i.e. how easily e- are able to be donated]

  1. CHARGE
    -vely charged ion = stronger Nu than conjugate acid
  2. X+ ELECTRONIC EFFECTS
    highly X- = weak Nu
    bonded to group 1 = strong Nu
  3. POLARISABILITY
    large Nu sites = strong Nu (Nu ability increases down group)
  4. SOLVATION
    anions more nucleophilic in polar APROTIC (anion and solvent don’t interact ∴ anion = more reactive)
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34
Q

what is polarisability?

A

how e- cloud distorts in electron field

e- tend to be drawn away from nucleus

larger atoms = more polarisable -> e- cloud more easily distorted

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35
Q

soft Nu

A

highly polarisable

-ve charge on large atoms

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36
Q

hard Nu

A

not as easily polarisable

-ve charge on small atoms

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37
Q

solvation

A

shell of protic solvent molecules around anion

reduces reactivity of anion

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38
Q

electrophilic strength

A

[i.e. how easily e- are accepted]

  1. CHARGE / STABILITY OF CATION
    +vely charged ion = stronger E than conjugate base
  2. X+ ELECTRONIC EFFECTS
    C bonded to high X- atoms = stronger E (larger δ+)
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39
Q

why is the behaviour of e- considered as quantum mechanics?

A

uncertainty about location and motion of a particular electron at a given time

= probability

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40
Q

why is a 2s AO larger than a 1s AO?

A

on average, an electron in a 2s AO is further away

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41
Q

nodal plane

A

where the probability of finding an e- = 0

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42
Q

what is the density of an electron in an AO proportional to?

A

square of AO

makes the probability of finding an e- in a particular region of space always +

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43
Q

what are completely filled shells called?

A

atomic core

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44
Q

what are partially filled shells called?

A

valence shells

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45
Q

what happens during covalent bonding?

A

AOs on different atoms overlap

e- pair up with opposite spins

46
Q

where does the electron density concentrate in MOs?

A

region between 2 nuclei, where AO overlap most

47
Q

why is the bonding MO lower in energy?

A

H2 molecule = more stable than 2 isolated H atoms

48
Q

σ bond

A

formed when 2 AOs overlap along interatomic axis

49
Q

𝛑 bond

A

formed when p AOs overlap sideways

50
Q

methane bonding

A

1 “2s” + 3 “2p” -> 4 sp3

51
Q

methyl cation bonding

A

1 “s” + 2 “p” -> 3 “sp2” (+ 2p)

52
Q

ethene

A

each carbon has 2 “sp2”, one σ bond and one 𝛑 bond

53
Q

ethyne

A

1 “s” + 1 “p” -> 2 “sp”

each C triple bond has one σ bond and two 𝛑 bond

54
Q

Bronsted-Lowry acid

A

a substance that donates a proton

55
Q

Bronsted-Lowry base

A

a substance that accepts a proton

56
Q

strong acid Ka/pKa relationship

A

large Ka ; lower pKa

57
Q

strong base Ka/pKa relationship

A

smaller Ka for conjugate acid ; higher pKa

58
Q

effect of EWG on acid strength

A

stabilises conjugate base (removes electron density from charged atom)

therefore more EWGs = stronger acid

59
Q

effect of EDGs on acid strength

A

destabilises conjugate base (adds electron density to charged atom)

therefore more EDGs = weaker acid

60
Q

Lewis acid

A

electron pair acceptor

61
Q

Lewis base

A

electron pair donator

62
Q

enantiomers

A

mirror images that can’t be super-imposed

63
Q

chiral

A

4 different groups attached

64
Q

diastereomers

A

not super-imposable + not mirror images

65
Q

substance containing single enantiomer =

A

enantiomerically pure

66
Q

substance containing equal amounts of both enantiomers =

A

racemic mixture / racemate

67
Q

clockwise rotation =

A

R

68
Q

anticlockwise rotation =

A

S

69
Q

properties of racemate compared to pure enantiomer

A

racemate has lower m.p

bc it’s a mixture

70
Q

gauche

A

large atoms = adjacent

71
Q

anti

A

large atom = opposite

72
Q

why can E/Z isomers be separated but not gauche/anti

A

E/Z rate of interconversion = 10^4 times slower (large barrier)

therefore can be separated

73
Q

which is more stable - E or Z?

A

E/trans

less steric repulsion

74
Q

enthalpy of formation

A

change in enthalpy required for the formation of a compound from its constituent elements in their natural states

under stander conditions - 25C + 1ATM

75
Q

small ΔG barrier

A

large k

fast reaction

76
Q

reaction coordinate

A

structural conversion of R -> P

i.e. bonds broken; angle of twist between groups

77
Q

where do the R/P lie on a reaction energy profile?

A

in energy minima

78
Q

which is the rate limiting step?

A

slowest step/highest Gibbs energy

79
Q

Hammond postulate

A

transition state for ENDO resembles PRODUCT

transition state for EXO resembles REACTANT

80
Q

low temp.

A

major product = one most easily formed (lowest reaction barrier)

not usually most stable

KINETIC control

81
Q

high temp.

A

initial product formed can go backwards + then overcome higher barrier

leads to equilibrium -> will then favour more stable product

THERMODYNAMIC control

82
Q

conjugation

A

overlap of p-orbitals across adjacent σ bonds

83
Q

when are double bonds more stable?

A

alternating pattern

sp2 = shorter + stronger (overlap so the bonds have more s character)

conjugation -> delocalised 𝛑 network

84
Q

why are tertiary carbocations the most stable?

A

electron donating inductive effect of alkyl groups

more R groups = more stabilisation

+ hyperconjugation

85
Q

hyperconjugation

A

interaction between σ-bonds with 𝛑/empty p orbitals

86
Q

when is stabilisation greatest between filled + empty orbitals?

A

when energy gap is smaller between the two

87
Q

nomenclature - carboxylic acids

A

prefix = carboxy

suffix = oic acid

88
Q

nomenclature - ester

A

prefix = alkoxycarbonyl

suffix = oate

89
Q

nomenclature - acid halide

A

prefix = haloformyl

suffix = oyl halide

90
Q

nomenclature - amide

A

prefix = carboamoyl

suffix = amide

91
Q

nomenclature - nitrile

A

prefix = cyano

suffix = nitrile

92
Q

nomenclature - aldehyde

A

prefix = formyl

suffix = al

93
Q

nomenclature - ketone

A

prefix = oxo

suffix = one

94
Q

nomenclature - alcohol

A

prefix = hydroxy

suffix = ol

95
Q

nomenclature - amine

A

prefix = amino

suffix = amine

96
Q

nomenclature - ether

A

prefix = alkoxy

suffix = ene

97
Q

nomenclature - alkene

A

prefix = alkenyl

suffix = ene

98
Q

nomenclature - alkyne

A

prefix = alkynyl

suffix = yne

99
Q

nomenclature - alkane

A

prefix = alkyl

suffix = ane

100
Q

nomenclature - halide

A

prefix = halo

101
Q

nomenclature - nitro

A

prefix = nitro

102
Q

principle quantum number (PQN)

A

shell

103
Q

angular momentum quantum number

A

shape

e.g. px or py or pz

104
Q

spin quantum number

A

up or down

105
Q

how are electron density maps produced?

A

x-rays are diffracted by interactions with e- rather than with protons/neutrons

sum of densities = map

106
Q

which side will be favoured in an acid/base reaction?

A

the side with the weaker acid/base combination

107
Q

how to work out hybridisation

A
  1. count atoms connected
  2. count lone pairs

4 = sp3
3 = sp2
2 = sp

108
Q

plane-polarised light

A

light whose electric field oscillates in just one plane

109
Q

how to distinguish between enantiomers

A

pass through plane polarised light

either rotate CW or ACW

chiral substance = optically active

110
Q

what does the angle of rotation depend on?

A

conc. of sample solution + length of cell containing it

111
Q

meso

A

enantiomers = identical

112
Q

practical measurements of E/Z isomer stability

A
  1. calorimetric measurement - measure enthalpy of hydrogenation of each isomer
  2. comparison of enthalpy of formation

Organic Chemistry (13 decks)

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