Structure and reactivity of organic molecules Flashcards

1
Q

heteroatoms

A

non metals on the periodic table which will be delta negative when bonded to carbon or hydrogen.

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2
Q

heteroatoms symbol

A

A

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3
Q

metals

A

atoms on the left side of the periodic table, including boron and silicon which will be delta positive when bonded to carbon or hydrogen.

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4
Q

metal symbols

A

M

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5
Q

order of electronegativity

A

M < H < C < A

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6
Q

explanation of carbon hydrogen bond polarity

A

carbons electronegativity is 2.6 and hydrogens is 2.2 so the difference in electronegativity is not enough to make a polar covalent bond.

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7
Q

delta negative atom in polar covalent bond

A

the atom which will have a greater pull on the bonding electrons and therefore is the nucleophile

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8
Q

delta positive atom in polar covalent bond

A

the atom which has a weaker pull on the bonding electrons and therefore is the electrophile.

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9
Q

what affects an atoms reactivity

A

dipoles from polar covalent bonds

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10
Q

hydritic definition

A

where a hydrogen will have a greater pull on the bonding electrons

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11
Q

protic definition

A

where a hydrogen will have a weaker pull on the bonding electrons.

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12
Q

LUMO characteristics

A

the LUMO is an electrophile, meaning it will accept electron pairs from electron rich sites such as nucleophiles.

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13
Q

HOMO characteristics

A

the HOMO is a nucleophile, meaning it will donate electron pairs to electron deficient sites such as an electrophile.

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14
Q

electron pairs on organic atoms

A

carbon has 4 bonding pairs
nitrogen has 3 bonding and 1 non bonding
oxygen has 2 bonding and 2 non bonding
halogens will have 1 bonding and 3 non bonding electron pairs

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15
Q

extra bond rule for organic atoms

A

an extra bond means a lone pair has formed a dative bond, resulting in a lone pair forming a bonding pair, giving the atom an extra positive charge.

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16
Q

fewer bonds rule

A

if there are fewer bonds on an atom than normal it means that the atom has formed an extra lone pair, which will result in an extra negative charge.

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17
Q

when can an atom form extra bonds

A

when the atom has a lone pair which it can use to form a dative covalent bond

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18
Q

cationic species properties

A

their positive charge will mean the ion will accept electron pairs more easily, making it a stronger Lewis acid and electrophile.

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19
Q

anionic species properties

A

their negative charge will mean that they will donate electron pairs more easily, meaning they will be a stronger Lewis base and nucleophile.

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20
Q

Lewis acid

A

An electron pair acceptor, and therefore an electrophile

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21
Q

Lewis base

A

An electron pair donator, and therefore a nucleophile

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22
Q

Bronsted base definition

A

An electron rich proton acceptor.

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23
Q

Bronsted acid definition

A

An electron deficient proton donator.

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24
Q

important orbital type in Bronsted acids

A

Lumo

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25
Q

important orbital type in Bronsted bases

A

Homo

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26
Q

reason that carbon has stronger bonds than silicon

A

carbon’s 2p orbitals will be smaller than silicon’s 3p orbitals, which will result in a larger relative area of overlap in carbons molecular orbitals than silicon’s molecular orbitals, resulting in shorter stronger bonds for carbon compounds allowing for carbon to form larger more complex molecules.

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27
Q

alcohol classifications

A

primary alcohols will have 1 carbon to carbon bond adjacent to the alcohol group.
secondary alcohols will have 2 carbon to carbon bonds adjacent to the alcohol group
tertiary alcohols will have 3 carbon carbon bonds adjacent to the alcohol.

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28
Q

amine classifications

A

primary means 1 N - C bond
secondary means 2 N - C bonds
tertiary means 3 N - C bonds.
quaternary means 4 N - C bonds

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29
Q

functional groups note

A

typically consisting of heteroatoms or carbon double/ triple bonds because they have pi electrons.

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30
Q

saturated molecule definition

A

where a molecule contains only sigma bonds

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30
Q

unsaturated definition

A

where a molecules contains a double or triple bond meaning it contains pi bonds.

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31
Q

unsaturated molecule types

A

Aryls
Alkene
Alkyne

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31
Q

alkyne functional group

A

c triple bond c

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31
Q

Aryl functional group

A

benzene ring attached to something

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32
Q

alkene functional group

A

c=c

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32
Q

alcohol functional group

A

OH

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33
Q

ether functional group

A

R - O - R

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34
Q

Amine functional group

A

N

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35
Q

Nitro compound functional group

A

N+=O
O-

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36
Q

aldehyde functional group

A

C = O
H

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37
Q

ketone functional group

A

C = O
R

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38
Q

carboxylic acid functional group

A

C = O
OH

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39
Q

ester functional group

A

C=O
O
C

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40
Q

acyl chloride functional group

A

C = O
Cl

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41
Q

Amide functional group

A

C =O
N

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42
Q

Acetal functional group

A

R - O - C - O - R

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43
Q

nitrile functional group

A

C triple bond N

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44
Q

acid anhydride functional group

A

C=O
O
C=O

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45
Q

oxidation classification

A

0 C - X
1 C - X
2 C - X
3 C - X
4 C - X

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46
Q

0 C - X

A

alkanes

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47
Q

1 C - X

A

molecules with 1 heteroatom bond + alkenes

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48
Q

2 C - X

A

molecules with 2 heteroatom bonds + alkynes

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49
Q

3 C - X

A

molecules with 3 heteroatom bonds

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50
Q

4 C - X

A

molecules with 4 heteroatom bonds

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51
Q

rules for oxidation classifications

A

look only at the atom with the highest number of C - X bonds to determine oxidation classification.

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52
Q

reduction definition

A

where there is a gain of electrons or hydrogen
where there is a loss of oxygen

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53
Q

oxidation definition

A

where there is a loss of electrons or hydrogen
where there is a gain oxygen

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54
Q

reason for alkenes being part of alcohol oxidation classification

A

one of the carbons in the unsaturated double bond will gain hydrogen, meaning it is reduced, whereas the other carbon in the unsaturated carbon to carbon double bond will gain a heteroatom, meaning it will be oxidized.
this will result in redox neutral reaction/ transformation.

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55
Q

reason that alkynes are part of the aldehydes classification

A

One of the carbons in the unsaturated carbon to carbon triple bond will gain 2 hydrogens meaning it will be reduced twice, whereas the other carbon will gain a double bond with an oxygen meaning it is oxidized twice.
this will result in a redox neutral transformation between any 2 C - X molecule and an alkyne.

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56
Q

priority naming rule

A

if there is multiple functional groups the group with the highest oxidation classification will go first, if they have the same priority then the group which comes first in the alphabet goes first.

57
Q

rule for choosing which side to go from when naming a molecule

A

name from the side which will give the highest priority group the lowest number.

58
Q

ortho

A

means 1,2 on cyclic structures

59
Q

para

A

means 1, 4 on cyclic structures

60
Q

meta

A

means 1, 3 on cyclic structures

61
Q

explanation for priority of electron donation in nucleophilic substitution

A

electron pairs will be donated from the HOMO meaning that the highest energy orbitals will be donated first meaning non bonding electrons first, then pi bonding orbitals, then sigma bonding orbitals.

62
Q

order of priority of electron donation

A

n - non bonding electron pair in hybridized P orbital
π - pi bonding orbital
σ - pi bonding orbital

63
Q

order of priority of electron receiving

A

P - unhybridized unoccupied P orbital
π* - antibonding pi orbital
σ* - antibonding sigma orbital

64
Q

Bond order formula

A

(bonding electrons - antibonding electrons) /2

65
Q

halogen bonding properties rule

A

as you go down the halogen group the greater the size of the valence P orbitals, which will result in a smaller relative overlap of when forming bonding molecular orbitals with another atom such as carbon, meaning as you go down the group the bond length will increase and the bond strength will decrease, which will result in halogens further down the group being more reactive.

66
Q

sp3 hybridisation rules

A

if the molecule only has single bonds it will be sp3
If you don’t know use VSEPR to check for tetrahedral structure.

67
Q

sp2 hybridisation rules

A

if the molecule has a double bond it will be sp2
If you don’t know check VSEPR for trigonal planar electron arrangement.

68
Q

sp hybridisation rule

A

if the molecule has a triple bond it will be sp hybridised
if you dont know check VSEPR and look to see whether it is linear.

69
Q

atoms which don’t hybridize

A

hydrogen because it only has 1 electron

70
Q

molecular orbital diagram process

A

draw out normal electronic configuration
draw out the hybridized electronic configuration
overlap valence hybrid orbitals and form appropriate bonding and antibonding molecular orbitals

71
Q

hybrid orbital energy explanation

A

sp3 orbitals will have higher energy than sp2 due to there being a greater ratio of P to S orbitals in sp3, meaning there is greater p character and the P orbitals will pull the degenerate hybrid orbitals further from the nucleus.

72
Q

nucleophilic substitution process

A

the electron pair from the non bonding occupied p orbital will attack the delta positive atom in the C - X bond which will allow the bonding electrons to shift onto the delta negative atom, breaking apart the C - X bond.

72
Q

Homolytic fission process

A

An electron in the bonding orbital will absorb energy from the electromagnetic spectrum ( typically UV light) which will promote the electron from the HOMO to the LUMO, meaning the electron will now sit in the lowest antibonding orbital, causing the bond to cleave.

73
Q

Isoelectric species definition

A

two species with the same number of electrons, which therefore have very similar electronic structures and chemical properties

74
Q

isoelectric carbocation

A

boron atom since a carbon atom with one less electron will have the same structure as boron.

75
Q

isoelectric carbanions

A

nitrogen because a carbon atom with an extra electron will have the same structure as nitrogen.

76
Q

conjugated system definition

A

A series of alternating single and double bonds which will allow for delocalized π electrons across many atoms bonding molecular orbitals.

77
Q

conjugated system properties

A

greater stability of molecule due to lower energy orbitals
lower HOMO to LUMO gap will mean a greater reactivity since electrons can more easily be promoted to the antibonding orbital.
colour can occur due to visible wavelengths of light being absorbed to promote electrons from the homo to the lumo.

78
Q

important features of conjugated systems

A

conjugated systems will allow for delocalized electrons, which will mean that resonance structures are possible.

79
Q

resonance structure definition

A

when delocalized electrons will travel between different atoms bonding orbitals meaning that the same molecule can constantly alternate between two different electronic structures.

80
Q

types of resonance structures

A

π - π*
n - π
p - π/ p - n
σ - π

81
Q

π - π* resonance

normal

A

π electrons from a double bond will travel to the π orbital of a single bond, forming a double bond.

π electrons from a double bond two bonds over from the original bond will travel to the π orbital of the single bond forming a double bond.

if no second single bond is available then the π electrons will form a non bonding electron pair on the atom, causing a positive and negative charge on the molecule.

82
Q

n - π resonance

A

electrons from the non bonding occupied p orbital will travel onto the unoccupied π orbital of the single bond.
π electrons from the double bond will travel onto the single bonds unoccupied π orbital forming a double bond.

if there is no available second single bond then the electrons will form a non bonding electron pair on the next atom.

83
Q

P - π/ P - n resonance name

A

mesomeric effect

84
Q

mesomeric effect resonance structure

A

electrons will move from the double bonds π orbital or the non bonding electron pairs occupied P orbital and occupy an unoccupied P orbital , causing one atom to gain a positive charge and another atom to lose a positive charge.

85
Q

σ - π conjugation names

A

positive inductive effect hyperconjugation

86
Q

σ - π resonance features

A

only occurs in secondary and tertiary carbocations

87
Q

σ - π resonance process

A

the R groups on the secondary or tertiary carbocation will have hydrogen σ bonds which will be parallel to the unoccupied P orbital, which will allow for the σ orbitals to give away their electrons partially, stabilizing the positive charge of the carbocation.

88
Q

Ka definition

A

the measure of how easily an acid will donate a proton to another species.

89
Q

pKa formula

A

pKa = -log Ka

90
Q

pKa relationship with Ka

A

as Ka increases the pKa decreases.

91
Q

acid base organic reaction

A

the non bonding electron pair on the base will go onto the delta positive hydrogen of the acid, meaning the electrons of the acid - hydrogen bond will go onto the acid, which will mean that the hydrogen will be donated to the base.

92
Q

conjugate base

A

the base of the reverse reaction, which is formed by the acid donating its proton

93
Q

conjugate acid

A

the acid of the reverse reaction - which is formed by the base accepting a proton.

94
Q

rule for strength of acids and bases

A

if the acid is a strong acid then the conjugate base must be a weaker base
if the base is a strong base then the conjugate acid must be a weaker acid.
vice versa

95
Q

strength of acid in relation to Ka and pKa explanation

A

ka is the measure of how easily an acid will donate its proton, which is to say how strong the acid is, so a high Ka means a strong acid, pKa is the negative log of Ka so a low pKa will mean a strong acid

96
Q

what is the effect of an anion being localized

A

localized anions electrons remain in fixed orbitals, meaning the anion will be more willing to give up its non bonding electron pairs, this will mean that the conjugate base will be stronger, meaning the acid will be weaker and therefore the acid will have a higher pKa

97
Q

delocalized anions effect on acid strength

A

a delocalized anion will have electrons which move freely between different bonding orbitals, which will mean these electron pairs will be donated less easily, resulting in a weaker conjugate base, which will result in a stronger acid and therefore a lower pKa

98
Q

structural / constitutional isomers

A

molecules with the same molecular formula, but a different connectivity of atoms and therefore different chemical properties

99
Q

possibilities for constitutional isomers

A

they have functional groups rearranged into different locations
they have different functional groups present

100
Q

stereoisomers definition

A

molecules with the same molecular structure and connectivity, but a different 3D arrangement in space.

101
Q

Enantiomers

A

two stereoisomers which are non superimposable mirror images of each other, with a stereogenic center

102
Q

different names for a stereogenic center

A

chiral center
stereo center

103
Q

stereogenic center definition

A

a carbon atom with 4 distinct groups attached to it.

104
Q

chirality requirements

A

a molecule is chiral if it contains a stereogenic center and has no planes of symmetry.

105
Q

rule for chirality of different stereoisomers

A

‘normal’ enantiomers must always be chiral
diasterioisomers can be chiral or non chiral
geometric isomers can never be chiral

106
Q

up position for stereoisomers

A

wedge coming out of the page

107
Q

down position for stereoisomers

A

hashed line going into the page

108
Q

configurations of stereoisomers definition

A

configurations are two different stereoisomers where bonds need to be broken and reformed to change between the two molecules.

109
Q

how to distinguish a configuration of stereoisomers

A

two different groups will be opposite each other in both enantiomers
if unsure make both molecules.

110
Q

conformations in stereoisomers definition

A

where there are two different structures of the same molecule with different energies and these different structures can be changed between by rotating bonds.

111
Q

R and S isomer distinguishing process

A

draw molecule and label the groups around the chiral center 1-4, 1 being the group with the highest atomic number, 4 being the group with the lowest atomic number.

flip the molecule around so the 4 group is in the down position.

rotate the steering wheel so that 1 is in the up position

if groups go 1-2-3 clockwise it is an R

if groups go 1-2-3 anticlockwise it is S

112
Q

R enantiomers

A

clockwise

113
Q

S enantiomer

A

anticlockwise

114
Q

enantiomers properties

A

enantiomers will have the same physicochemical and spectroscopic properties in normal environments

115
Q

racemic mixtures definition

A

where there is a mixture of two enantiomers of equal proportions.

116
Q

α D = 0 meaning

A

the molecule doesn’t rotate polarized light

117
Q

α D = 0 examples

A

racemic mixtures
geometric isomers
Anti - diasterioisomers when there is a plane of symmetry.

118
Q

why does α D = 0 in Anti - diasterioisomers when there is a plane of symmetry.

A

when there is a plane of symmetry in Anti - diasterioisomers it means the RS and SR configurations are identical, meaning they wont rotate polarized light.

119
Q

α D in R and S rule

A

there is no relationship between R and S and +ve or-ve values, but if R is +30 then S is -30

120
Q

number of enantiomers formula

A

2^x
where x is the number of stereogenic centers.

121
Q

diasterioisomers definition

A

stereoisomers with 2 stereogenic centers which are not mirror images but have distinct relative configurations.

122
Q

diasterioisomers chirality

A

if the molecule has no plane of symmetry it will be chiral from two different stereogenic centers
if the molecule has a plane of symmetry it will be achiral.

123
Q

syn

A

RR configuration or SS configuration

124
Q

anti

A

RS configuration or SR configuration

125
Q

anti - diasterioisomers when there is a plane of symmetry

A

the RS and SR enantiomers will be identical molecules

126
Q

geometric isomers

A

molecules containing a bond with restricted rotation.

127
Q

E

A

geometric isomers with highest priority groups on opposite sides

128
Q

Z

A

geometric isomers with highest priority groups on the same side

129
Q

cis

A

same side highest priority in cyclic structures

130
Q

trans

A

opposite side highest priority in cyclic structures

131
Q

difference in energy for conformations rule

A

the greater the energy required for a bond top be rotated, the greater the difference in energy between two different conformations.

132
Q

energy required to rotate different types of bond

A

single bonds have low energy for rotation.
π - π conjugations will have a medium energy for rotation due to the delocalized π electrons giving the bond double bond character
n - π conjugations will have high energy for rotation due to the delocalized electrons giving the single bond a high double bond character.
double bonds have impossible rotational energy.

133
Q

Newman diagram

A

face on looking down the bond axis

134
Q

sawhorse/ perspective diagram

A

side on looking at the bond axis in the y axis of the page.

135
Q

staggered antiperiplanar structure

A

x groups are 180 degrees away from each other, lowest energy conformation due to 6 σ 6σ* hyperconjugations.

136
Q

staggered gauche conformation

A

x groups 60 degrees away from each other, medium energy conformation due to 6 σ 6σ* hyperconjugations.

137
Q

elliptical syn periplanar structure

A

0 degrees between x groups, highest energy conformation due to 3σ 3σ destabilizations.

138
Q

cyclohexane configurations

A

chair and boat
chair is the low energy configuration
boat is the high energy configuration

139
Q

chair conformation structure of hydrogens

A

one hydrogen will be axial up and one hydrogen will be equatorial down
or one hydrogen will be axial down and one hydrogen will be axial up

140
Q

axial hydrogens

A

hydrogens which are vertical

141
Q

equatorial hydrogens

A

hydrogens which are almost horizontal

142
Q

changing between different conformation

A

change an axial group to an equatorial group

143
Q

changing between different configurations

A

change an up position to a down position