T6: Organic Chemistry I Flashcards
(79 cards)
1
Q
What are hydrocarbons?
A
Molecules made of hydrogen and carbon only
2
Q
What is meant by homologous series?
A
Compounds with the same functional group but different carbon chain length (family)
Carbon chain length refers to the same genral formula
e.g. alkanes, alkenes, alcohols etc.
3
Q
What is a functional group?
A
- the most reactive part of any compound
- carries out all the reactions
4
Q
What is a saturated hydrocarbon?
A
Compound that contains no C=C double bond
Positive result in Br water test: no change - remains orange
5
Q
What is an unsaturated hydrocarbon?
A
Compound that contains at least one C=C double bond
Positive result for Br water test: orange to colourless
6
Q
What is the general formula for alkenes?
A
7
Q
What is the general formula for alkanes?
A
8
Q
What is the general formula for alcohols?
A
9
Q
What is meant by molecular formula?
A
The actual number of atoms of each element in a molecule
10
Q
What is meant by empirical formula?
A
The simplest whole number ratio of atoms of each element in a compound
11
Q
What is meant by displayed formula?
A
Shows how all the atoms are arranged, and all the bonds between them
12
Q
Define but-
A
- 4 carbons
13
Q
What are the steps to naming compounds?
A
- longest unbranched chain
- the syllable after the root tells you whether there are any double bonds e.g. -ane , -ene
- Duplication of any side groups - Di (2) , Tri (3)
14
Q
Define meth-
A
- 1 carbon
15
Q
What is meant by skeletal formula?
A
Shows the bonds of the carbon skeleton only with any functional groups
16
Q
What is meant by structural formula?
A
Shows the arrangement of carbon by carbon with attached hydrogens and functional groups
17
Q
Define eth-
A
- 2 carbons
18
Q
Define prop-
A
- 3 carbons
19
Q
Define pent-
A
- 5 carbons
20
Q
Define hex-
A
- 6 carbons
21
Q
Define hept-
A
- 7 carbons
22
Q
Define non-
A
- 9 carbons
23
Q
Define dec-
A
- 10 carbons
24
Q
Define oct-
A
- 8 carbons
25
In terms of organic reactions, what is addition?
Joining two or more molecules together to form a larger molecule
26
In terms of organic reactions, what is polymerisation?
Joining together lots of simple molecules (monomer) to form a giant molecule (polymer)
27
In terms of organic reactions, what is elimination?
When a small group of atoms breaks away from a larger molecule
28
In terms of organic reactions, what is substitution?
When one species is replaced by another
29
In terms of organic reactions, what is hydrolysis?
Splitting a molecule into two new molecules by adding H+ and OH- derived from water
30
In terms of organic reactions, what is oxidation?
Any reaction in which a species loses electrons
31
In terms of organic reactions, what is reduction?
Any reaction in which a species gains electrons
32
What is a mechanism?
* diagrams that break reactions down into individual stages to show how substances react together
* a curly arrow - used to show how electron pairs move when bonds are made/broken
33
What are the different types of mechanisms?
* Radical substitution of halogens in alkanes -halogenalkanes
* Electrophilic addition of halogens and hydrogen halides to alkenes - halogenalkanes
* Nueclophilic substitution of primary halogenalkanes with aqueous potassium hydroxide - alcohols and with ammonia - amines
34
What are nucleophiles?
* electron pair donors (negatively charged ions)
* like to react with positive ions
* attracted to electron "poor
## Footnote
In terms of nucleophillic substitution:attracted to the Cδ+ atom in a polar carbon-halogen bondthe bond breaksnucleophile replaces halogen
35
What are electrophiles?
* electron pair acceptors (positively charged ions)
* like to react withnegative ions
* attracted to electron "rich" areas
## Footnote
In terms of electrophile addition:e.g. HBr (electrophile) - attracted to the C=C double bondpolarises HBr until it breaksmoldcule joins alkene
36
What are radicals?
* unpaired electrons
* attack any molecule (negative/positive/neutral)
* very reactive
## Footnote
In terms of free radical substitution:
* e.g. choline atoms produced when UV light splits a Cl two molecule
37
What are structural isomers?
* general (umbrella) term
* the molecular formula is the same
* the structural formula is different
| Inlcudes: Chain isomers, Positional isomers & Functional group isomers
38
What are chain isomers?
* same molecular formula
* carbon skeleton can be arranged differently
* similar chemical properties
* different physical properties
39
What are positional isomers?
* same molecular formula
* skeleton and functional group could be the same
* functional group is attached to different carbon atom
* different physical properties
* chemical properties may vary
40
What are functional group isomers?
* same molecular formula
* same atoms arranged into different functional groups
* very different physical & chemical properties
41
What are alkanes?
Saturated hydrocarbons
42
What is the general formula for cycloalkanes?
43
What is bond fission?
*Breaking a covalent bond (a single covalent bond is a shared pair of electrons between two atoms)
44
What is heterolytic fission?
* the bond breaks unevenly
* one of the bonded atoms receives both electrons
* a positive & negative cation can be formed
45
What is homolytic fission?
* the bond breaks evenly
* each bonding atom receives one electron
* two electrically uncharged radicals are formed
46
What is the condition of photochemical reactions?
UV light
47
What does the reaction of halogens and alkanes produce?
Halogenalkanes
48
What is the reaction of alkanes and halogens also known as?
Free radical substitution reaction
49
What are the three stages of a reaction mechanism?
1) Initiation - radicals are produced
2) Propagation - radicals are used and created
3) Termination - radicals are destroyed
50
What are the initiation steps in a general free radical substitution reaction?
* Initiation
1) Cl - Cl bond is broken by UV light - photodissociation
2) The bond evenly splits - homolytic fission, a *Cl radical is formed
51
What are the propagation steps in a general free radical substitution reaction?
* Propagation
1) *Cl attacks (alkane) molecule
2) The new alkyl radical attacks another Cl two molecule
3) The new * Cl radical can continue to attack the alkane molecule until both are used up
52
What are the termination steps in a general free radical substitution reaction?
* Termination
1) Free radicals join together to form a stable molecule
2) Some products formed will be trace impurities in the final sample
53
What can crude oil be referred as?
Petroleum
54
What is crude oil?
A mixture of short and long chain alkanes
55
What process is used to separate crude oil?
Fractional distillation
56
How does fractional distillation work?
57
What is cracking used for?
* to break heavy fractions to make smaller molecules - high demand (e.g. petrol and naphtha)
* involves breaking the C-C bonds
58
What are the two types of cracking?
* Thermal cracking
* Catalytic cracking
59
How does thermal cracking work?
* cracking using high temperatures (up to 1000°C) and pressures (up to 70atm)
* produces lots of alkenes
* valuable products/high demand
59
How does thermal cracking work?
* cracking using high temperatures (up to 1000°C) and pressures (up to 70atm)
* produces lots of alkenes
* valuable products can be made (polymers-->plastics)/high demand e.g petrol --> better fuel
60
How does catalytic cracking work?
* zeolite catalyst (hydrated aluminosilicate)
* moderate temperatures & pressures
* produces aromatic hydrocarbons and motor fuels
61
Why is using a catalyst beneficial?
* cuts costs as the reaction can be done at lower temperatures and pressures
* speeds up the reaction - saving time
62
What is knocking?
Alkanes explode of their own accord when the fuel/air mixture in the engine is compressed
63
How can knocking be made less likely?
Adding branched chains and cyclic hydrocarbons to the fuel mixture
64
What is meant by "reforming" ?
Converting straight-chain alkanes into branched chain alkanes and cyclic hydrocarbons
65
What catalysts can be used when reforming?
Platinum stuck on aluminium oxide (Pt)
66
What can alkanes be used as?
Fuels
67
What does the complete combustion of an alkane produce?
Carbon dioxide and water
68
What does the incomplete combustion of an alkane produce?
Carbon monoxide, carbon and water
69
What physical state is required for combustion?
Gas - liquid alkanes will need to be vaporised
70
Why are smaller alkanes easier to burn
Smaller alkanes turn into gases more easily (more volatile) so they'll burn more easily
71
Why are alkanes good fuels?
They release a lot of energy when burnt
72
What type of reaction is combustion?
Exothermic
73
Give examples of alkanes used as fuels
* Methane - central heating & cooking
* Kerosene - jet fuel
74
Give examples of fossil fuels
* coal
* oil
* natural gas
75
Wha are advantages of using fossil fuels?
* easily accessible
* cheaper
* generates electricity for transport and heating
76
What are the disadvantages using fossil fuels?
* non-renewable
* harmful emissions
77
What harmful emissions might be produced through combustion?
* Carbon Monoxide - toxic
* Sulfur Dioxide and Oxides of Nitrogen leas to acid rain
78
What is the role of catalytic convertors?
They remove (some) pollutants from car emissions
