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A Level Chemistry- KE > Organic Chemistry I > Flashcards

Organic Chemistry I Flashcards

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1
Q

what is a hydrocarbon?

A

compound of hydrogen and carbon only

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2
Q

what is meant by homologous series?

A

organic compounds with same functional group + general formula

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3
Q

what is meant by functional group?

A

group of atoms in a molecule responsible for the characteristic reactions of that compound

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4
Q

what is addition?

A

joining of two or more molecules to make a larger molecule

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5
Q

what is substitution?

A

one species getting replaced by another

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6
Q

what is hydrolysis?

A

splitting a molecule into 2 new molecules by adding H+ and OH- derived from water

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7
Q

what is oxidation?

A

any reaction where a species loses electrons

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8
Q

what is reduction?

A

any reaction where a species gains electrons

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8
Q

what is the general formula for alkenes?

A

CnH₂n

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9
Q

what is the general formula for alkanes?

A

CnH₂n+2

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9
Q

are alkanes and cycloalkanes saturated or unsaturated?

A

saturated because they have single carbon bonds

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10
Q

what is the general formula for cycloalkanes?

A

CnH₂n

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11
Q

are alkenes and cycloalkenes saturated or unsaturated?

A

unsaturated because the double bond which allows them to make bonds with extra atoms in addition reactions

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12
Q

what test is used to identify the presence of a C=C bond?

A

-shake alkene with brown bromine water
and it should quickly decolourise
-this is because bromine is added across the double bond to form colourless dibromoalkane

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13
Q

halogen + alkene?

A

dihalogenoalkane

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14
Q

what is an electrophile?

A

electron-pair acceptors (electron poor so attracted to electron rich areas)

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15
Q

what is a nucleophile

A

electron-pair donors (electron rich so attracted to electron poor areas)

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16
Q

what is a radical?

A

-species with an unpaired electron (in mechanisms represented with a single dot)
-result of homolytic fission of a covalent bond

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17
Q

what is an isomer?

A

molecules with the same molecular formula but are arranged differently

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18
Q

what are the types of structural isomerism?

A

chain, positional, functional group

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19
Q

what is a chain isomer?

A

carbon skeleton can be arranged differently e.g. straight or branched

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20
Q

what properties are similar or different in chain isomers?

A

physical properties are different (e.g. boiling point) ,, branched chains do not pack closely together so intermolecular forces are weaker– lower bp

chemical properties are similar

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21
Q

what is a positional isomer?

A

functional group is attached to a different carbon atom

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22
Q

what properties are similar or different in positional isomers?

A

both chemical and physical properties are different

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23
Q

what is a functional group isomer?

A

when the same atoms are arranged into different functional groups

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24
Q

what properties are similar or different in functional group isomers?

A

both have very different physical and chemical properties

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25
Q

can atoms rotate around c-c bonds?

A

yes,, don’t be fooled something that looks like an isomer may not actually be one if the function group is attached to the same carbon in a different position

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26
Q

what is stereoisomerism?

A

have the same structural formula but a different arrangement in space,, only in double bonds

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27
Q

can double bonds rotate c=c?

A

no, because of the overlap of the p orbitals in an alkene to form a pi bond

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28
Q

what is cis isomerism?

A

Z,, on the same side (double bond only)

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29
Q

what is trans isomerism?

A

E,, opposite side (double bond only)

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30
Q

why do alkenes have stereoisomerism?

A

because of the lack of rotation within the double bond

31
Q

what is a Z isomer?

A

same group on same side

32
Q

what is an E isomer?

A

same group on opposite side

33
Q

what do you need to do when naming stereoisomers?

A

put E/Z/cis/trans

34
Q

what happens if all the groups are different in stereoisomerism?

A

atoms with a larger atomic number are given priority

35
Q

what is homolytic fission?

A

-bond breaks evenly and each bonding atom receives one electron which is unpaired forming radicals

36
Q

why are radicals highly reactive?

A

because of the unpaired electron

37
Q

what is heterolytic fission?

A

-bond breaks unevenly so one of the bonding atoms receives both electrons from the bonded pair
-two different substances are formed e.g. cation or anion

38
Q

what is a primary alcohol?

A

has one R-group

39
Q

what is a secondary alcohol?

A

has two R-groups

40
Q

what is a tertiary alcohol?

A

has three R-groups

41
Q

what is a primary halogenoalkane?

A

one alkyl group

42
Q

what is a secondary halogenoalkane?

A

two alkyl groups

43
Q

what is a tertiary halogenoalkane?

A

three alkyl groups

44
Q

what is a halogenoalkane?

A

alkanes with at least one halogen atom

45
Q

when can halogenoalkanes be classified into primary, secondary and tertiary?

A

if they have just one halogen atom

46
Q

how do alkenes form polymers?

A

through addition polymerisation

47
Q

how can chemists limit the problems caused by polymer disposal?

A

-developing biodegradable polymers
-removing toxic waste gases caused by incineration of plastics

48
Q

what conditions do photochemical reactions require?

A

UV (light)

49
Q

how do halogens react with alkenes to from halogenoalkanes?

A

photochemical reactions using UV light then radical substitution

50
Q

what are the three stages of radical substitution?

A

initiation, propagation, termination

51
Q

what happens during the initiation step of radical substitution?

A

-radicals are produced (photodissociation)
-diatomic halogen bond splits equally and each atom keeps one electron (homolytic fission)
-atom becomes highly reactive radical due to unpaired electron

52
Q

what happens during the propagation step of radical substitution?

A

-radicals are used up and created in a chain reaction
-radical attacks alkane forming alkane radical
-alkane radical attacks second halogen molecule
-new halogen radical can attack another alkane molecule until all the non radicals are wiped out

53
Q

what happens during the termination step of radical substitution?

A

-two free radicals join together to form a stable molecule
-there are many possible termination reactions

54
Q

what bonds does an alkene have?

A

both sigma and pi bonds (like hot dog) sigma bond sandwiched between pi bond

55
Q

which has a higher electron density pi or sigma and how is it formed?

A

sigma bonds,, two orbitals overlap in a straight line in the space between two atoms giving highest possible electron density=strong electrostatic attraction=highest bond enthalpy

56
Q

how is a pi bond formed?

A

two lobes of two orbitals overlap sideways making the electron density more spread out as it is above and below the nuclei=weaker electrostatic attraction

57
Q

what does adding hydrogen to a C=C bond produce?

A

an alkane- ethene will react with hydrogen gas to produce ethane but only in the presence of a nickel catalyst at a temp of 150 C

58
Q

why do electrophilic addition reactions happen to alkenes?

A

the double bond has lots of electrons so attracts electrophiles which are electron pair accepting e.g. positive ions like H+

58
Q

what is a carbocation?

A

organic ion containing positively charged carbon atom

59
Q

how is margarine formed from vegetable oil?

A

by the catalytic hydrogenation of unsaturated vegetable oil double bonds are removed ∴ raising the melting point of the oil so it is solid at room temperature

60
Q

how are halogenoalkanes formed from alkenes?

A

alkenes undergo electrophilic addition with hydrogen halides

61
Q

how are dihalogenoalkanes formed from alkenes?

A

-halogen reacts with alkenes by electrophilic addition
-halogens add across the double bond and each of the carbon atoms ends up bonded to a halogen

62
Q

how are alcohols formed by alkenes?

A

alkenes are hydrated by steam at 300 C and pressure of 60-70 atm with an acid catalyst

63
Q

how are alkenes made with acidified potassium dichromate?

A

shake alkene with acidified potassium dichromate and the purple solution is decolourised then the alkene has been oxidised and a diol (alcohol with two -OH) is made

64
Q

what are the products of incomplete combustion?

A

C, CO2, H2O

65
Q

what are the products of complete combustion?

A

CO2, H2O

66
Q

what is crude oil made from?

A

alkanes

67
Q

how can crude oil be made useful?

A

by fractional distillation- it turns crude oil into useful fractions

68
Q

how can different alkanes in crude oil can be separated by fractional distillation?

A

different alkanes have different boiling points due to the different carbon chain lengths

69
Q

how are alkane molecules attracted to each other?

A

by intermolecular forces

70
Q

are alkanes polar or non-polar?

A

non-polar because carbon and hydrogen have similar electronegativites

71
Q

are alkanes soluble in water?

A

no, alkanes have no permanent dipoles so cannot form hydrogen bonds

72
Q

why are alkanes generally unreactive?

A

because of the strong covalent bonds between hydrogen and carbon

73
Q

what happens when alkanes are combusted (burned with enough oxygen)?

A

products are CO2 and water (gas forms)

74
Q

what happens when alkanes are combusted (burned with little oxygen)?

A

incomplete combustion- carbon monoxide, water, carbon are products (may still be some CO2)

75
Q

how do catalytic converters solve the problems caused by pollutants?

A

-stop engines releasing pollutants such as carbon monoxide, oxides of nitrogen and unburnt hydrocarbons using a platinum catalyst to change the harmful pollutants to harmless gases e.g. water vapour and nitrogen and less harmful ones like CO2

76
Q
A

A Level Chemistry- KE (15 decks)

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