module 4 - core organic chemistry Flashcards
(71 cards)
1
Q
different ways of presenting molecules
A
- empircal
- molecular
- displayed
- structural
- general
- skeletal
2
Q
general formula of alkanes
A
CnH2n+2
3
Q
structural formular of butane
A
CH3CH2CH2CH3
4
Q
displayed formular of ethanol
A
H H
/ /
H—-C———C—O—-H
/ /
H H
5
Q
skeletal formular of butan-2-ol
A
draw
6
Q
homologus series
A
organic compounds that have the same functional group but each successive member differs by CH2
7
Q
functional group
A
group of atoms responsible for characteristic reactions of a compound
8
Q
example of a functional group
A
COOH
9
Q
alkyl group general formula
A
CnH2n+1
10
Q
aliphatic
A
compound containing carbon and hydrogen joined together in straight chains, branched chains or non-aromatic rings
11
Q
alicyclic
A
aliphatic compound arranged in non-aromatic rings with or without side chains
12
Q
aromatic
A
a compound containing a benzene ring
13
Q
amine displayed formula
A
H
/
-N
\
H
14
Q
aldehyde molecular formula
A
-CHO
15
Q
difference between saturated and unsaturated hydrocarbons
A
saturated - single c-c bonds only and saturated with hydrogens
unsaturated - presence of multiple c-c double bonds.
16
Q
isomerism
A
where molecules exist with the same molecular formula, with a different structural formula
17
Q
two types of isomerism
A
structural
stereo
18
Q
3 types of structural isomers
A
position
functional group
chain
19
Q
how are covalent bonds broken
A
homolytic fission
heterolytic fission
20
Q
homolytic fission
A
bond splits equally - free radicals formed
21
Q
heterolytic fission
A
atom receives both electrons from bonding pair
22
Q
radical
A
species with unpaired electron
23
Q
curly arrow represents…
A
movement of electron pair, showing either heterolytic fission or formation of a covalent bond
24
Q
why does the boiling point of alkanes increase as the molecule gets bigger
A
- more electrons
- stronger london forces which require more energy to break
25
what are alkanes
- saturated hydrocarbons containing single c-c and c-h bonds as σ bonds
26
what are σ bonds
end on end overlap of the sp2 orbital
27
bond angle of alkanes
109.5
28
shape of alkanes
tetrahedral shape
29
which alkane has a higher boiling point : straight chain or branched
- straight chain alkanes have higher boiling points than branched alkanes
- molecules can get closer making more points of contact for london forces to occur, so more energy is required to break these forces
30
why are reactions of alkanes limited
due to lack of polarity of alkane σ bonds
31
what reactions do alkanes go under
combustion reactions
free radical substitution
32
reactivity of alkanes
- relatively unreactive
- non polar
- very low polarity of σ bonds present
33
uses of alkanes
fuels - readily available, easy to transport, burns to release no toxic products
34
incomplete combustion of alkanes can produce ...
carbon monoxide
35
dangers of carbon monoxide
- colourless, odourless + highly toxic.
- binds irreversibly with haemoglobin in rbc to form carboxyhaemoglobin preventing oxygen passing round body.
36
three steps of free radical substitution
initiation
propagation
termination
37
what are the only two reactants that can react together in a free radical substitution
a halogen atom and an alkane
38
reaction of chlorine with methane
full reaction:
CH4(g) + Cl2(g) -> CH3Cl(g) + HCl(g)
initiation:
Cl2 ---> (UV) 2Cl*
propagation:
CH4 + Cl* -> CH3* + HCl
CH3* + Cl2 -> CH3Cl + Cl*
termination:
2Cl*-> Cl2
2CH3 -> C2H6
Cl* + CH3* -> CH3Cl
39
reaction of bromine with methane
full reaction:
CH4(g) + Br2(g) -> CH3Br(g) + HBr(g)
initiation:
Br2 ---> (UV) 2Br*
propagation:
CH4 + Br* -> CH3* + HBr
CH3* + Br2 -> CH3Br + Br*
termination:
2Br*-> Br2
2CH3 -> C2H6
Br*+ CH3* -> CH3Br
40
limitations of free radical substitutions
- collisions are uncontrollable so can't make one particular product
- further substitutions can happen
- if unwanted product is made, expensive separation will be required
- reactions at different positions in a carbon chain
41
what are alkenes
- unsaturated hydrocarbons containing c-c double bonds
- double bond comprised of a σ bond and π bond
42
what is a π bond
- sideways overlap of p orbitals
43
longer chain alkenes =
less volatile than shorter chain cause there's more electrons, more and stronger london forces, requiring more energy to break
44
more branched alkenes =
more volatile than less branched - can't pack closely, less points of contact, less london forces, requires less energy to break
45
explanation of shape of alkenes
trigonal planar shape 120
- three bonding pair of electrons are in plane of molecule and repel each other (electron pair repulsion)
- The fourth π bonding pair forms double bond in combination with carbon-carbon σ bond
46
stereoisomerism
compounds with the same structural formula but with a different spatial arrangements
47
presence of a double bond can create two possible structures. what are they
cis structure
trans structure
48
how does E/Z isomerism occur
- if the C=C double bond is quite rigid and prevents freedom of rotation
- 2 different atoms or groups on each carbon atom of the double bond
49
when is E/Z naming applied
when there are 3/4 different substituents
50
difference between E/Z isomerism and cis/trans isomerism
cis/trans isomerism is used when the groups attached to both the carbons are the same
E/Z isomerism is used when there is 3 or 4 different groups are attached to each carbon
51
what is the name of the rule used to identify E/Z stereoisomers
cahn-ingold-prelog (cip)
52
cip rules
- atom with the higher atomic number has the higher priority
- if atoms or groups are the same, next point of connection is considered
53
name of mechanism in which alkenes react
electrophilic addition
54
reactivity of alkenes in terms of relatively low bond enthalpy of π bond
- π bond occurs above and below the two nuclei so weaker attraction
- the π electrons are more exposed than the σ bond so they're more prone to electrophilic attack
55
4 addition reactions of alkenes
hydrogenation
halogenation
hydrohalogenation
hydration
56
addition reaction of hydrogen in presence of a suitable catalyst
hydrogenation:
- H2 and Ni catalyst necessary
- 150°C
- alkene -> alkane
57
addition reaction of halogens to form dihaloalkanes, including qualitative test
halogenation:
- add bromine water to sample
- presence of alkene = orange -> colourless
58
addition reaction of hydrogen halides to form haloalkanes
hydrohalogenation:
-HX has a permanent dipole
- Hδ⁺ is the electrophile
- Pair of e⁻s attracted from π bond
- Heterolytic fission of H-X bond
- Carbocation formed (C⁺)
- X⁻ now a nucleophile
- single halogen atom added to the molecule
59
addition reaction of steam in the presence of an acid catalyst
hydration:
- h2o , 300°C
- H3PO4 (catalyst)
- alkene -> alcohol
- industrial prep of alcohol
60
product of hydrogenation
alkene -> alkane
61
product of halogenation
dihaloalkane
62
product of hydration
alcohol
63
electrophile
electron pair acceptor
- an atom or group of atoms that is attracted to an electron-rich centre and accepts an electron pair
- usually positive ion or contains atom with partial positive charge (δ⁺)
64
electrophilic addition in alkenes by heterolytic
hx has a permanent dipole
- hδ⁺ is the electrophile
- pair of e⁻s attracted from π bond
- heterolytic fission of H-X bond
- carbocation formed (C⁺)
- x⁻ now a nucleophile
- single halogen atom added to the molecule
65
rule that predicts formation of a major organic product
markovnikov's rule
66
markovnikov's rule
- halide ion will always add to most stable carbocation
- number of carbon atoms attached to carbocation decides stability
67
more carbons attached to carbocation =
more stable
68
conditions needed for polymerisation
high pressure, heat and a catalyst
69
benefits and limitations of sustainability of processing waste polymers by combustion for energy production
- combustion removes the polymers and can generate power as an additional benefit - thereby saving fossil fuels.
- toxic products of some polymers and polymers that contain chlorine would create HCl as a waste gas which contributes to acid rain
- this process still causes environmental pollution as carbon within polymer can be released as carbon dioxide contributing to global warming
70
benefits of sustainability of processing waste polymers by use as organic feedstock for production of plastics
- chemical feed-stock recycling breaks down polymers without separating them = forms simple gases that can then be used to manufacture pure, fresh polymers
- waste polymers broken down, by chemical and thermal processes, into monomers, gases and oils
- products are then used as raw materials in production of new polymers and other organic chemicals
71
limitations of sustainability of processing waste polymers by removal of toxic waste products
- use of landfill sites = not ideal
