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CHEM 110 > Block 1 - Foundations > Flashcards

Block 1 - Foundations Flashcards

(67 cards)

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1
Q

Heteroatoms

A

Any atom not C or H

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2
Q

Second and third bond strength relative to first bond

A

Second bond (and third) must be weaker than the first

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3
Q

Covalent bonds form when…

A

… atomic orbitals overlap to form molecular orbits

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4
Q

Atomic orbital overlaps can be…

A
  1. Good (end-on), i.e. sigma bonds (σ-bonds)
  2. Weak (side-on), i.e. pi bonds (π-bonds aka DBEs)

Pi bonds weaker than sigma bonds

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5
Q

Single, double, triple bonds (σ or π)

A

Single: 1 sigma bond –> inert
Double: 1 sigma bond, 1 pi bond –> reactive
Triple: 1 sigma bond, 2 pi bonds

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6
Q

Hybridisation

A

The mixing of atomic orbitals belonging to the same atom, but having slightly different energies so a redistribution of energy takes place between them –> results in the formation of new orbitals of equal energies and identical shape

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7
Q

Rotation around double and triple bonds - π bonds

A

Rotation about double and triple bonds would require breaking a π-bond –> incurs significant energy penalty

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8
Q

C bonded to 4 atoms (single bonds)

A

Geometry: Tetrahedral (109.5°)
Hybridisation: sp3

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9
Q

C bonded to 3 atoms (two single bonds, one double bond)

A

Geometry: Trigonal planar (120°)
Hybridisation: sp2

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10
Q

C bonded to 2 atoms (one single bond, one triple bond OR two double bonds)

A

Geometry: Linear (180°)
Hybridisation: sp

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11
Q

Periodic table: First 20 elements

A

H, He, Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca

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12
Q

Periodic trends: Electronegativity, ionisation energy, atomic radius

A

Electronegativity: Increases up and right
Ionisation energy: Increases up and right
Atomic radius: Decreases up and right

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13
Q

Isomers

A

Compounds with same molecular formula, but different arrangement in space

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14
Q

Constitutional isomers

A

Different sequence of bonds

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15
Q

Double bond equivalents (DBEs) = ½ (2n4 + n3 - n1 + 2)

where…

A

DBE = ½ (2n4 + n3 - n1 + 2)
where n4 = C, n3 = N, n1 = H or halogens
O doesn’t appear in DBE formula

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16
Q

Stereoisomers

A

Different arrangement of groups in space

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17
Q

Conformational isomers

A

Differ by rotation about a single bond

No bond breaking required

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18
Q

Configurational isomers

A

Interconversion requires breaking bonds

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19
Q

Enantiomers

A

Non-superimposable mirror images
Stereogenic centre (C)
Chiral

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20
Q

Diastereomers

A

Not mirror images

Non-superimposable

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21
Q

Types of isomers

A

Isomers –> Constitutional and Stereoisomers
Stereoisomers –> Conformational and Configurational
Configurational –> Enantiomers and Diastereomers

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22
Q

Define conformer

A

The conformation of a molecule; a particular shape it adopts as a result of rotation about bonds

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23
Q

Conformational isomers - types of projection

A 
Sawhorse projection (views molecules from an oblique angle)
Newman projection (views molecules end-on)
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24
Q

Interconversion of conformers

A

Staggered —rotate 60°—> Eclipsed

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25
Staggered conformers vs Eclipsed conformers
Staggered: atoms fit 'between' other atoms, most stable Eclipsed: atoms fit directly 'behind' other atoms, least stable
26
Types of staggered and eclipse conformers
Staggered; anti-conformer: most stable Eclipsed Staggered; gauche-conformer Eclipsed; syn-conformer: least stable
27
Cyclohexane conformers
Bond 109° preferred --> not flat/planar Boat Chair
28
Chair conformers: types of H atoms
Axial: pointing vertically up or down Equitorial: point in other directions
29
Lowest energy conformation
Chair conformer
30
Ring flip
Converting from 'Chair A' to 'Chair B' | Where all axial groups become equatorial groups and vice versa
31
Generally, the favoured conformer for substituted cyclohexanes have the largest atom(s)/group(s) in the ______
Equatorial
32
CIP rules
Determines whether E or Z configuration | Higher atomic number = higher priority = ranks higher
33
E vs Z configuration
``` Divide horizontally (i.e. like --------) E-configuration: two higher priority groups are on opposite sides of double bond Z-configuration: two higher priority groups are on same side of double bond ```
34
Stereogenic centre
Asymmetric carbon
35
Achiral
Where sp3 C has two identical atoms/groups attached so molecule is superimposable
36
Chiral
Where sp3 C has different atoms/groups attached so molecule is non-superimposable on its mirror image
37
Racemic mixture
1:1 ratio (equal amounts) of enantiomers | Rotates light equally in both directions --> overall rotation is zero
38
R vs S configuration
R: priority of highest substituents decreases in a clockwise direction S: priority of highest substituents decreases in an anti-clockwise direction
39
Enantiomers, identical/meso and diastereomers
Enantiomers: mirror images, non-superimposable Identical/meso: mirror images, superimposable Diastereomers: not mirror images, non-superimposable
40
If octane is attached to something, it's called ____
Stemane
41
CH3O name
Methoxy
42
Naming cycloalkanes
Add 'cyclo' to front of name, e.g. cyclopentane
43
Double bonds are more readily polarised due to...
The relative mobility of pi electrons, i.e. C=O is more polar than C-O bond
44
Branching and bpt
IF strongest when molecules are in close proximity, so decreased branching = increased bpt as molecules can stack closer together
45
Similar vs different molecular weights - bpt
Similar M: more polar functional groups = higher bpt | Different M: difference in temporary dipole-dipole interactions that has greatest effect on bpt
46
Polarity and water solubility
More polar = more water soluble (hydrophilic) | Less polar = more lipid soluble (lipophilic)
47
Polar stationary phase: Polar vs non-polar solutes
Polar solutes are more attracted to the polar stationary phase and move slowly Non-polar solutes are less attracted to the polar surface of stationary phase and so move more rapidly
48
Which molecule has higher bpt question - key points
1. If similar size = similar dispersion forces 2. Most polar bonds 3. Strongest IM interactions (what is it) Therefore, highest bpt
49
Which molecule moves fastest on chromatography column - key points
1. Least polar molecule 2. No polar bonds 3. Interacts least with polar stationary phase Therefore moves fastest on chromatography column
50
Types of curly arrows
Half arrow = 1 electron moving | Full arrow = 2 electrons moving
51
Homolytic bond cleavage
One electron from the bond ends up on each of the atoms which were formally bonded (i.e. covalent bond cleaves symmetrically)
52
Heterolytic bond cleavage
Both electrons from the bond end up on one of the atoms which were formally bonded (i.e. covalent bond cleaves asymmetrically)
53
If 'A' is more electronegative than C, what happens? | CH3C-A
Bonds will break: CH3C+ + A- (carbocation + anion) e.g. A = Cl, O, Br
54
If 'A' is less electronegative than C, what happens? | CH3C-A
Bonds will break: CH3C- + A+ (carbanion + cation) e.g. A = metal
55
Geometry of carbocations
Planar (sp2 hybridised)
56
Relative stability of carbocations
Tertiary > Secondary > Primary > Methyl
57
Classes of reaction + sub-classifications
Substitution Addition Elimination Polar/non-polar (radical) Involving a nucleophilic/electrophilic reagent Nature of substrate (alkyl, acyl, aryl)
58
Substitution reactions
Where one atom/group is replaced by another through breaking and formation of sigma bonds
59
Addition reactions
A pi-bond breaks, and is replaced by 2 sigma bonds
60
Elimination reactions
Two sigma-bonds break, and one pi-bond forms
61
Reaction mechanism
The detailed pathway by which reactants are converted to products Often requires multiple steps (elementary reaction) that occur sequentially
62
Reactive intermediates
Species involved in a reaction mechanism that may be unstable or short-lived
63
Nucleophilic substitution
Reagent is a nucleophile SN1 occurs step-wise (bond-breaking then bond-forming) SN2 occurs in a single step (bond-breaking/forming simultaneous)
64
Nucleophile
Electron rich --> electron donor Can be neutral or negatively charged Have either lone pairs of e- or e- in pi-bonds
65
Electrophile
Electron deficient --> electron acceptor | Can be neutral or positively charged
66
Polar reaction occurs when...
A nucleophile reacts with an electrophile to form a new covalent bond
67
The terms cis and trans are used to describe...
The relative position of substituents on a ring

CHEM 110 (6 decks)

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