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

4.1 Basic concepts and hydrocarbons Flashcards

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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
Q

elimination reaction definition

A

removal of a small molecule from a larger one

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26
Q

effect of chain length on boiling point

A

longer chain length = larger surface area = more surface contact possible between molecules = greater London forces = more energy required to overcome forced

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27
Q

effect of branching on boiling point

A

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
Q

why alkanes don’t react with most common reagents

A

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
Q

complete combustion of alkane

A

alkane + oxygen -> carbon dioxide + water

30
Q

incomplete combustion of alkanes

A

alkane + oxygen -> carbon monoxide + water + carbon particulates

31
Q

reaction of alkanes and halogens

A

alkane + halogen -> haloalkane + hydrogen halide

only in the presence of sunlight

32
Q

radical substitution definition

A

substitution reaction involving free radicals as a reactive intermediate

33
Q

alkane substituion method

A

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
Q

limitation of radical substitution

A

many products formed

have to separate desired product from everything else

35
Q

alkene definition

A

unsaturated hydrocarbon

contains double bond

36
Q

how double bond prevents rotation of carbon atoms

A

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
Q

shape around double bond

A

trigonal planar
three regions of electron density
repeal each other as much as possible
no lone pairs

38
Q

stereoisomer definition

A

same structural formula, different arrangement of atoms in space

39
Q

why stereoisomerism occurs

A

rotation restricted around double bond

groups attached to each carbon atom fixed relative to each other

40
Q

cis-trans isomerism requirements

A

has double bond

each carbon in double bond attached to two different groups (one must be hydrogen on each carbon)

41
Q

E/Z isomerism requirements

A

C=C double bond

different groups attached to each carbon atom of C=C bond

42
Q

how to predict E/Z isomerism

A

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
Q

bond enthalpies in C=C

A

sigma bond = 347 kJ mol^-1

pi bond = 265 kJ mol^-1

44
Q

why alkenes are more reactive than alkanes

A

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
Q

hydrogenation of alkenes

A

alkene + hydrogen -> alkane
requires nickel catalyst
423 K

46
Q

halogenation of alkenes

A

alkene + halogen -> haloalkane
room temperature
used as test for unsaturation

47
Q

hydration of alkenes

A

alkene + steam -> alcohol
requires phosphoric acid catalyst
2 possible products if unsymmetrical alkene (use Markownikoff)

48
Q

addition reaction of alkenes with hydrogen halides

A

alkene + hydrogen halide -> haloalkane
room temperature
2 possible products if unsymmetrical alkene (use Markownikoff)

49
Q

electrophilic addition

A

addition reactions that form saturated compounds

50
Q

electrophile definition

A

(group of) atom(s) attracted to electron rich-centre
accepts electron pair
usually positive ion or has partial positive charge

51
Q

mechanism of reaction between but-2-ene and hydrogen bromide

A

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
Q

mechanism of reaction between propene and bromine

A

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
Q

Markownikoff’s rule

A

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
Q

carbocation stability

A

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
Q

repeat unit of polymer

A

double bond opens up
square brackets
put “n” at bottom left of right bracket (shows large number of repeats)

56
Q

environmental concerns of waste polymers

A

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
Q

recycling benefits

A

conserves finite fossil fuels

decreases waste going to landfill

58
Q

why polymers have to be sorted

A

mixed polymers renders product useless (different properties)

59
Q

why PVC hard to recycle

A

high chlorine content and additives

when burnt, hydrogen chloride (corrosive) and toxic dioxins produced

60
Q

how PVC is recycled

A

solvents dissolves polymer, high-grade PVC recovered by precipitation from solvent, solvent used again
PVC grinded and reused to manufacture new products

61
Q

why polymers can be used as fuel

A

derived from fossil fuels
have high stored energy value
fossil fuels incinerated, generating steam to drive a turbine producing electricity

62
Q

feedstock recycling definition

A

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
Q

biodegradable polymers

A

broken down by microorganisms into water, carbon dioxide, biological compounds
made from starch or cellulose

64
Q

monomer

A

molecule that can be bonded to other identical molecules to form a polymer

65
Q

compostable polymers

A

degrade and leave no visible or toxic residues

66
Q

photodegradable polymers

A

contain bonds that are weakened by absorbing light to start the degradation

A-Level Chemistry (12 decks)

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