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A-Level Chemistry > 4.1 Basic concepts and hydrocarbons > Flashcards

4.1 Basic concepts and hydrocarbons Flashcards

1
Q

homologous series definition

A

series of organic compounds having the same functional group, with each successive member differing by CH2

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2
Q

functional group definition

A

group of atoms responsible for the characteristic reactions of a compound

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3
Q

alkyl group definition

A

of formula CnH2n+1

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4
Q

aliphatic definition

A

compound containing carbon and hydrogen joined together in straight chains, branched chains or non-aromatic rings

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5
Q

alicyclic definition

A

aliphatic compound arranged in non-aromatic rings with(out) side chains

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6
Q

aromatic definition

A

compound containing a benzene ring

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7
Q

benzene ring definition

A

functional group where carbon atoms are bounded to each other by alternating single and double bonds

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8
Q

saturated definition

A

containing only single bonds

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9
Q

unsaturated definition

A

containing multiple carbon-carbon bonds and aromatic rings

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10
Q

structural isomers definition

A

another compound with the same molecular formula but with different bonds between them

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11
Q

general formula definition

A

simplest algebraic formula of a member of a homologous series
e.g. CnH2n+2

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12
Q

structural formula definition

A

minimal detail showing arrangement of atoms in a molecule

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13
Q

displayed formula definition

A

relative position of atoms and the bonds between them

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14
Q

skeletal formula definition

A

simplified organic formula
shown by removing hydrogen atoms from alkyl chains
just carbon skeleton and associated functional group

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15
Q

structural isomer definition

A

compounds with same molecular formula but different structural formulae

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16
Q

types of covalent bond fission

A

heterolytic fission

homolytic fission

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17
Q

heterolytic fission definition

A

one bonding atom receives both electrons from bonded pair

forms cations and anions

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18
Q

homolytic fission definition

A

each bonding atom receives one electron from bonded pair

forms 2 radicals

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19
Q

radical definition

A

species with an unpaired electron

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20
Q

“curly arrow” uses

A

movement of an electron pair

shows heterolytic fission or formation of covalent bond

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21
Q

alkane definition

A

saturated hydrocarbon
contains single C-C bonds and C-H bonds as sigma bonds
free rotation of sigma bond

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22
Q

reaction mechanism definition

A

how a reaction takes place

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23
Q

addition reaction definition

A

two reactants join together to form one product

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24
Q

substitution reaction definition

A

atom or group of atoms is replaced by a different atom or group of atoms

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25
elimination reaction definition
removal of a small molecule from a larger one
26
effect of chain length on boiling point
longer chain length = larger surface area = more surface contact possible between molecules = greater London forces = more energy required to overcome forced
27
effect of branching on boiling point
more branches = less surface points of contact between molecules = fewer London forces also branches get in the way and prevent molecules from getting closer together as straight chain molecules
28
why alkanes don’t react with most common reagents
C-C and C-H sigma bonds are strong C-C bonds are non-polar electronegativity of C and H are very similar (can be considered non-polar)
29
complete combustion of alkane
alkane + oxygen -> carbon dioxide + water
30
incomplete combustion of alkanes
alkane + oxygen -> carbon monoxide + water + carbon particulates
31
reaction of alkanes and halogens
alkane + halogen -> haloalkane + hydrogen halide | only in the presence of sunlight
32
radical substitution definition
substitution reaction involving free radicals as a reactive intermediate
33
alkane substituion method
initiation -homolytic fission of halogen molecules form radicals (1 step) propagation - radicals attack alkane (2 steps) termination - two radicals combine to form molecule and reaction end (3 steps)
34
limitation of radical substitution
many products formed | have to separate desired product from everything else
35
alkene definition
unsaturated hydrocarbon | contains double bond
36
how double bond prevents rotation of carbon atoms
contains sigma bonds (direct overlap of orbitals directly between bonding atoms) contains pi-bonds (sideways overlap of adjacent p-orbitals above and below bonding atoms) pi-bond restricts rotation and locks bonding atoms in place
37
shape around double bond
trigonal planar three regions of electron density repeal each other as much as possible no lone pairs
38
stereoisomer definition
same structural formula, different arrangement of atoms in space
39
why stereoisomerism occurs
rotation restricted around double bond | groups attached to each carbon atom fixed relative to each other
40
cis-trans isomerism requirements
has double bond | each carbon in double bond attached to two different groups (one must be hydrogen on each carbon)
41
E/Z isomerism requirements
C=C double bond | different groups attached to each carbon atom of C=C bond
42
how to predict E/Z isomerism
higher atomic number of group = higher priority highest priority groups on same side = Z highest priority groups on opposite sides = E Cahn-Ingold-Prelog (CIP) rules
43
bond enthalpies in C=C
sigma bond = 347 kJ mol^-1 | pi bond = 265 kJ mol^-1
44
why alkenes are more reactive than alkanes
double bond made up of sigma bond and pi bond | pi bond’s electrons more exposed (on outside of double bond) so breaks more readily
45
hydrogenation of alkenes
alkene + hydrogen -> alkane requires nickel catalyst 423 K
46
halogenation of alkenes
alkene + halogen -> haloalkane room temperature used as test for unsaturation
47
hydration of alkenes
alkene + steam -> alcohol requires phosphoric acid catalyst 2 possible products if unsymmetrical alkene (use Markownikoff)
48
addition reaction of alkenes with hydrogen halides
alkene + hydrogen halide -> haloalkane room temperature 2 possible products if unsymmetrical alkene (use Markownikoff)
49
electrophilic addition
addition reactions that form saturated compounds
50
electrophile definition
(group of) atom(s) attracted to electron rich-centre accepts electron pair usually positive ion or has partial positive charge
51
mechanism of reaction between but-2-ene and hydrogen bromide
hydrogen bromide polar molecule as bromide more electronegative electron pair in pi bond attracted to partially positive hydrogen atom (breaks double bond) bond forms between hydrogen atom and carbon atom (forms carbocation) H-Br bond breaks (heterolytic fission) and forms bromide anion bromide anion reacts with carbocation (opposite charges), forms addition product
52
mechanism of reaction between propene and bromine
bromine approaches alkene pi bond electrons causes induced dipole in bromine pi bond electrons attracted to partial positive end of bromine (breaks double bond) bond formed between carbon atom of double bond and bromine atom (forms carbocation) Br-Br bond breaks (heterolytic fission), forming bromide anion carbocation reacts with bromide anion (oppositely charged) to form addition product
53
Markownikoff’s rule
in a hydrogen halide + alkene reaction, most stable carbocation (the one with the most alkyl groups attached) will be formed for the halide ion to bond to
54
carbocation stability
more alkyl groups (R) = more stable alkyl groups push electrons towards positively-charged carbocation positive charge is spread out between alkyl groups, making ion more stable
55
repeat unit of polymer
double bond opens up square brackets put “n” at bottom left of right bracket (shows large number of repeats)
56
environmental concerns of waste polymers
polymers more readily available, cheap to purchase and convenient than better alternatives e.g. glass bottles not very reactive, non-biodegradable so stays and impacts environment (wildlife)
57
recycling benefits
conserves finite fossil fuels | decreases waste going to landfill
58
why polymers have to be sorted
mixed polymers renders product useless (different properties)
59
why PVC hard to recycle
high chlorine content and additives | when burnt, hydrogen chloride (corrosive) and toxic dioxins produced
60
how PVC is recycled
solvents dissolves polymer, high-grade PVC recovered by precipitation from solvent, solvent used again PVC grinded and reused to manufacture new products
61
why polymers can be used as fuel
derived from fossil fuels have high stored energy value fossil fuels incinerated, generating steam to drive a turbine producing electricity
62
feedstock recycling definition
chemical and thermal processes that reclaim monomers, gases or oil from waste polymers product similar to ones produced from crude oil refineries able to handle unsourced and unwashed polymers
63
biodegradable polymers
broken down by microorganisms into water, carbon dioxide, biological compounds made from starch or cellulose
64
monomer
molecule that can be bonded to other identical molecules to form a polymer
65
compostable polymers
degrade and leave no visible or toxic residues
66
photodegradable polymers
contain bonds that are weakened by absorbing light to start the degradation

A-Level Chemistry (12 decks)

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