Lectures 9-21 Flashcards
(163 cards)
1
Q
drawing Lewis Structures
A
sum valence electrons, place single bond between atoms, complete octet rules, add lone pairs/multiple bonds, place extra electrons in d orbitals if necessary
2
Q
the more resonance structures a molecule has,
A
the more stable it is
3
Q
bond order
A
0.5 x (number of delocalised electrons/number of bonds containing delocalised electrons)
4
Q
Lewis Acids
A
can accept a pair of unbonding electrons
5
Q
all species with an odd number of electrons are
A
radicals
6
Q
number of electron pairs: linear
A
2
7
Q
number of electron pairs: trigonal planar
A
3
8
Q
number of electron pairs: tetrahedral
A
4
9
Q
number of electron pairs: trigonal bipyramidal
A
5
10
Q
number of electron pairs: octahedral
A
6
11
Q
linear bond angle
A
180
12
Q
trigonal planar bond angle
A
120
13
Q
tetrahedral bond angle
A
109.5
14
Q
trigonal bipyramidal bond angle
A
90, 120 and 180
15
Q
octahedral bond angle
A
90 and 180
16
Q
lone pairs occupy
A
more space than bonding pairs
17
Q
2 lone pairs, 2 bonds
A
bent
18
Q
3 bond pairs, 1 lone pair
A
trigonal-pyramidal
19
Q
2 bond pairs, 1 lone pair
A
V-shaped
20
Q
Lewis Structures are useful for
A
electron counting and description of bonding
21
Q
molecular shape considers that lone pairs
A
push actual atoms in certain ways
22
Q
trigonal bipyramidal with one lone pair molecular shape
A
see-saw
23
Q
octahedral with one lone pair molecular shape
A
square pyramid
24
Q
octahedral with two lone pairs molecular shape
A
square planar
25
Molecular Orbital
orbital overlap
26
sigma bond
covalent bond for two electrons; elongated, ellipse shape
27
when a bond forms, energy is
released
28
sp3 hybrid orbitals are
tetrahedral
29
C-C bond is weaker than
C-H bond
30
structural isomers differ in
connectivity
31
isopropyl
-CH(CH3)2
32
tert-Butyl
-C(CH3)3
33
average bond order
bonds / # resonance structures
34
double and triple bonds in geometry only count as
one electron pair
35
formal charge (where valence electrons means from original atom)
valence electrons - # lone pair electrons - 1/2(# bonding electrons)
36
we number chain closest to
branch point
37
conformational isomers
differ due to bond rotation
38
bond rotation slows with
cooling
39
Newman Projection
looking down with carbons in a row
40
dihedral angle
angle between front and back hydrogen/group when looking at a molecule via Newman Projection
41
staggered
most stable conformation; hydrogens/groups as far apart as possible
42
eclipsed
least stable conformation; increase in potential energy
43
torsional strain
bonds-electron repulsion
44
in eclipsed conformation, there is more
torsional strain
45
antiperiplanar staggered
`most stable for butane; two methyl groups as far apart from each other as possible
46
gauche staggered
methyl groups at 60 degrees; steric strain
47
anticlinal eclipsed
eclipsed but methyl groups not close for butane
48
synperiplanar eclipsed
methyl groups as close as they can be to each other; steric and torsional strain
49
bigger substituents near each other,
higher energy (gauche/eclipsed)
50
to calculate conformer energy values,
add up gauche/eclipsed values between ALL groups (use table)
51
chiral
molecules that have a non-superimposable mirror image
52
stereoisomers
same numbers and types of atoms, differ in three-dimensional space
53
asymmetric carbon atom
stereogenic centre
54
enantiomers
pairs of non-superimposable mirror image molecules
55
racemate
1:1 mixture of enantiomers
56
in a 1:1 mixture of enantiomers, rotation of plane polarised light would be
zero
57
enantiomers rotate plane polarised light in
opposite directions
58
optically active
a compound that rotates plane polarised light
59
enantiomers have the same physical and chemical characteristics except
in their behaviour towards plane polarised light and their reactivity in a chiral environment
60
specific rotation [alpha]D
alpha/l x c
61
assigning absolute configuration about an asymmetric carbon
priority based on decreasing atomic number, viewing molecule along bond from asymmetric carbon to lowest priority
62
priority #1 atomic number is at
bottom
63
if clockwise, denoted as
R
64
if anticlockwise, denoted as
S
65
phantom atoms
if a carbon is double bonded to an atom, we treat it as a single bond to two of this atom
66
the more H atoms a carbon is bonded to,
the lower in priority
67
number of stereoisomers
2^n, where n is number of asymmetric centres
68
mirror images will have reversed
S and R
69
diastereoisomers
stereoisomers that are not enantiomers
70
S cancels
R
71
meso compound
stereoisomer with two or more asymmetric carbon atoms that is NOT chiral
72
ring strain
angle strain, torsional strain, steric strain
73
highest ring strain energy
cyclopropane
74
lowest ring strain energy
cyclohexane
75
preferred cyclohexane conformation
chair
76
all bonds in chair conformation are
staggered, so torsional strain is eliminated
77
axial hydrogens
parallel to axis that goes through centre of ring vertically
78
equatorial hydrogens
radiate out from equator of ring
79
rings on cyclohexane should be in
equatorial position
80
why should rings in cyclohexane be equatorial?
1,3-diaxial steric interaction
81
groups on same face of cycloalkane
cis
82
groups on different face of cycloalkane
trans
83
groups remain cis or trans even when they
flip between axial and equatorial
84
bigger group should be
equatorial
85
ax-eq and eq-ax are identical if
the substituents are the same
86
cis is higher in energy for fused cyclohexanes because
one carbon is axial
87
you cannot ring flip
trans-decalin cyclohexane
88
the more stable/conformationally rigid fused cyclohexane
trans-decalin
89
hybridised orbital for trigonal planar/double bonds
sp^2
90
hybridised orbital for tetrahedral
sp^3
91
pi bond
bond between two carbon atoms where we’ve formed a sigma bond and we’re overlapping two p orbitals side-on
92
pi region is
electron-rich
93
in the pi region, electrons are not as
tightly held
94
sigma bond is stronger than
pi bond
95
no rotation about a
pi bond
96
geometric isomers form due to to
inability of double carbon-carbon bonds to rotate
97
we number chain giving the double/triple bond the
lowest number/top priority
98
Z
of substituents of higher priority are on the same side of the double bond
99
E
if substituents of higher priority are on different sides of the double bond
100
which types of alkenes are less stable, cis or trans?
cis
101
steric strain is present in
cis alkenes
102
cumulated/allenes
consecutive double bonds
103
conjugated
double-single-double
104
isolated
double-single-single-single-etc.-double
105
bonds with partial double bond character will be
shorter
106
partial double bond character is present in
conjugated systems
107
conjugated systems are
more stable
108
benzene is comprised of a
continuous pi cloud circuit with partial double bond character throughout the entire loop
109
resonance stabilisation
electrons are delocalised in pi cloud
110
ortho/o
1,2
111
meta/m
1,3
112
para/p
1,4
113
naming benzenes with more than two substituents
number substituents to give lowest possible numbers, list alphabetically
114
when do we number benzenes according to the chain
if the chain attached to the benzene has more than six carbons
115
constitutional isomer
same molecular formula, different structure
116
double bonds are composed of
one sigma bond and one pi bond
117
all atoms directly attached to double bond will be
coplanar
118
aromatic compounds
planar, cyclic, conjugated, Huckel's rule
119
Huckel's rule
4n + 2 pi electrons where n is a whole number
120
sp hybridised
linear, triple bonds
121
each sp bond contains
two pi bonds and one sigma bond
122
primary carbon
carbon bonded to one carbon
123
secondary carbon
carbon bonded to two carbons
124
tertiary carbon
carbon bonded to three carbons
125
quaternary carbon
carbon bonded to four carbon
126
benzylic carbon
carbon directly attached to a carbon of a benzene ring (sp^3)
127
aryl carbon
carbon part of benzene ring (sp^2)
128
vinylic carbon
carbon that is part of a double bond (sp^2)
129
allylic carbon
carbon bonded to a carbon-carbon double bond carbon (bonded to a vinylic carbon, sp^3)
130
primary alcohol
hydroxyl carbon bonded to one other carbon
131
secondary alcohol
hydroxyl carbon bonded to two other carbons
132
tertiary alcohol
hydroxyl carbon bonded to three other atoms
133
ether
oxygen atom bonded to two carbons
134
ether nomenclature
add ether on the end with a space; alkyl groups are substituents
135
thiol
sulphur bonded to carbon and hydrogen
136
thiol nomenclature
add 'thiol' on end
137
primary amine
N attached to one carbon
138
secondary amine
N attached to two carbons
139
tertiary amine
N attached to three carbons
140
alcohol has priority over
amine group
141
nitrogen has a lone pair which can be
donated in acid-base reactions
142
C=O bond
sigma C-O bond, pi C-O bond
143
carboxylic acids have priority over
alcohols and amines
144
primary amide
N is attached to two hydrogens and C=O
145
secondary amide
N is attached to one H, one R group and the C=O
146
tertiary amide
C=O is attached to two R groups and the C=O
147
nitriles
carbon-nitrogen triple bonds
148
polar bonds arise from
electronegativity differences
149
in polar bonds, partial positive charge is equal in magnitude to
partial negative charge
150
dipole moment
degree of polarity
151
dipole moment units
Debye (D)
152
dipole moment points towards
negative end of whole molecule
153
where there is symmetry/the negative ends cancel out, there will be
no net dipole moment
154
cis and trans isomers can have different
polarities
155
in the C=O atom, the pi bond/cloud is distorted towards the
O atom
156
dispersion forces
due to instantaneous/temporary dipole forces
157
attraction in dispersion forces is between
positive nucleus and negative electron cloud
158
dispersion forces increase with
size of atom
159
states of non-polar electron can be understood by the strength of
dispersion forces
160
alkanes have strong
dispersion forces
161
more branched molecules have weaker
dispersion forces
162
lone pairs contribute to hydrogen bonding by providing
localised centres of negative charge
163
if the oxygen is not attached to a hydrogen, it
cannot engage in hydrogen bonding
