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Chemistry AS (2015) > 1.7 introductory organic chemistry > Flashcards

1.7 introductory organic chemistry Flashcards

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1
Q

1b: Complete 5 molecule drawings generated from the spreadsheet.

A

How many did you get right? Rank below:

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2
Q

1c: What is the difference between a hazard and a risk?

A

a risk is the likelihood of a hazard

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3
Q

2a: What is an alkane?

A

a saturated hydrocarbon (only has C and H with single bonds)

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4
Q

2a: What is the general formula of alkanes?

A

CnH2n+2

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5
Q

2b: What are isomers?

A

molecules with the same molecular formula but a different structural formula

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6
Q

2c: What are alkanes generally used for?

A

fuels

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7
Q

2c: Whence are alkanes obtained?

A

crude oil

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8
Q

2c: How is a certain alkane extracted from crude oil? (2)

A

fractional distillation

cracking and reformation

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9
Q

2d: Why are alkanes a good source of fuel? (2)

A

provide a lot of energy

we already have the methods and equipment

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10
Q

2d: Why should we have alternative sources of fuel besides alkanes? (2)

A

non-renewable source (crude oil)

CO2 produced from combustion, affecting climate change

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11
Q

2e: What are the products of combustion of a hydrocarbon? (2)

A

CO2, H2O

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12
Q

2e: What is a free radical?

A

an unstable molecule

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13
Q

2e: Name the stages of free radical substitution. (3)

A

initiation
propagation
termination

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14
Q

2e: Describe the initiation stage of free radical substitution (halogen + alkane).

A

one C-H bond splits, making the hydrocarbon a radical (e.g. CH3CH3 -> CH3CH2. + H.)

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15
Q

2e: Describe the propagation stage of free radical substitution (halogen + alkane).

A

one of the halogen atoms breaks off and joins onto the hydrocarbon radical (e.g. CH3CH2. + Cl2 -> CH3CH2Cl + Cl.)

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16
Q

2e: Describe the termination stage of free radical substitution (halogen + alkane).

A

every radical joins with another radical until there is none left (e.g. Cl. + H. -> HCl)

17
Q

2e: How do you represent the movement of an electron when drawing the mechanism of a free radical reaction?

A

a single-headed curly arrow from the bond to an atom

18
Q

2e: Why does a free radical reaction have more products than expected?

A

the radicals can join onto any other radical, so for example the substitution of chlorine into ethane can also give butane and hydrogen as well as chloroethane and HCl

19
Q

3a: What is the general formula of alkenes?

A

CnH2n

20
Q

3a: What is an alkene?

A

an unsaturated hydrocarbon with one carbon-carbon double bond

21
Q

3a: Describe the structure of a double bond.

A

consists of a pi bond (single covalent bond between two sp3 orbitals) and a sigma bond (between two p orbitals; they bend to create arcs either side of the pi bond)

22
Q

3b: Describe cis-trans isomerism.

A

in a cis molecule, the heaviest groups (e.g. methyl, ethyl) are both on the same side of the double bond; they are opposite in a trans molecule

23
Q

3b: Why does cis-trans isomerism occur?

A

restrictive rotation (the C=C double bond cannot rotate)

24
Q

3c: Describe E-Z isomerism.

A

similar to cis-trans; comes into effect when atoms besides C and H are involved - E = opposite, Z = same - and is decided by atomic number

25
Q

3di: addition CnH2n + H2 ->

an alkene + hydrogen goes to… with catalyst…

A

CnH2n+2

an alkane; catalyst Ni

26
Q

3dii: addition CnH2n + F2 ->

an alkene + halogen goes to…

A

CnH2nF2

a di-sub halogenoalkane

27
Q

3diii: addition CnH2n + HCl ->

an alkene + hydrogen halide goes to…

A

CnH2n+1Cl

a mono-sub halogenoalkane

28
Q

3div: addition CnH2n + O2 ->

an alkene + oxygen goes to… with catalyst…

A

CnH2n(OH)2

a diol; catalyst K2MnO4

29
Q

3ei: Identify and describe the mechanism of the reaction between HBr and C2H4

A

electrophilic addition
HBr is polarised, so H end is pulled towards the double bond in ethene
this takes out an electron, creating a Br. radical
the H joins to the ethene, creating an ethyl radical
eventually a Br. radical attaches to the ethyl

30
Q

3ei: Identify and describe the mechanism of the reaction between Br2 and C2H4

A

electrophilic addition
Br2 becomes polarised near the double bond
the delta+ end pulls an electron from the bond
the Br-Br bond splits, creating a Br. radical and C2H4Br. radical
these eventually join

31
Q

3eii: In one stage of an electrophilic addition reaction between H. and .CH2.CHCH2, where does the H. join on and why?

A

the one at the end; it is less stable as there are fewer nearby covalent bonds to provide stability

32
Q

3f: Describe the test for a C=C bond.

A

bromine water: orange -> colourless

33
Q

3f: What is the equation of the test for a C=C bond (using ethene an asn example)?

A

C2H4 + 1/2Br2 + OH -> C2H4BrOH

34
Q

3g: Describe the mechanism of addition polymerisation.

A

initiator Q-Q splits to give Q. Q.
Q. interacts with CnH2n to split the double bond and create a .CnH2nQ radical
this reacts with another CnH2n and so on to create a chain
eventually the other Q. reacts with the end of the chain to finish the reaction

Chemistry AS (2015) (17 decks)

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