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Chemistry 2.0 > 3.4 Alkenes > Flashcards

3.4 Alkenes Flashcards

1
Q

What are the reagents for electrophilic addition and the electrophile in the reaction
Why is the reaction and addition reaction because

A

HCL and Br
Electrophile : HBr
A hydrogen and bromine atom have been added to

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2
Q

Why is tertiary carbocations more stable than secondary carbocations

A

There is a greater positive inductive effect from three alkyl groups in tertiary carbocations compared to two alkyl groups in secondary carbocations

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3
Q

Reagent of electrophilic addition with halogens

A

Reagents : Cl2 and Br2

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4
Q

Bromine reacts with alkenes even though bromine is a non polar molecule. Explain why bromine molecules react with double bonds in alkenes

A
  • C=C bond is electron rich
  • and induces a dipole in Br2
  • delta positive and delta negative are attracted to C=C double bond
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5
Q

Reagents of electrophilic addition with sulphuric acid

A

Reagent : H2S04

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6
Q

Reagents and conditions of a reaction from alcohol to alkene and state mechanism and state role of H2SO4

A
  • elemination mechanism
  • heat with concentrated sulfuric acid
  • H2SO4 is reproduced as a catalyst
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7
Q

Reagents of direct hydration and conditions

A

Reagents : H2O
Conditions : Concentrated H3PO4 as a catalyst

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8
Q

Describe bonding in an alkene double bond

A
  • one bond form overlap of s orbitals
  • second bond focuses from overlap of p orbitals
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9
Q

How to know if it’s electrophilic addition

A

Alkene turns into Haloalkane

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10
Q

Explain why 2-bromopentane is a major product and 1 - bromopentane is a minor product

A

2-bromopentane formed from a secondary carbocation
1 - bromopentane formed from a primary carbocation
Secondary carbocation is more stable than primary carbocation due to positive inductive effect of the two alkyl groups

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11
Q

Explain why there are no major or minor products when chlorine is reacted with but-1-ene

A

Because a Cl is added on either side, there is only one combination they can react in

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12
Q

StatI role of sulphuric acid when it reacts with ethanol

A

H2S04 is regenerated so it acts as a catalyst

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13
Q

Butan-2-ol reacts with concentrated sulfuric acid. Idenfity role of sulfuric acid and name method that is used to seperate products.

A

Role : oxidising agent
Method : fractional distillation

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14
Q

Concentrated sulfuric acid reacts with sodium chloride. State observation of the reaction and role of sulfuric acid

A

Observation : White/misty/steamy fumes
Role : Acid/proton donor

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15
Q

Concentrated sulfuric acid reacts with sodium iodide to produce several prodcuts. Observations made during this reaction include the formation of a black solid a yellow gas and gas with smell of bad eggs.
State what the smell is, yellow gas is and state what black solid is

A

Black solid : iodine
Yellow gas : Sulfur
Gas : Hydrigen sulfite

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16
Q

Student failed to fill burette correctly so gap between tap and tip of burette still contained air. Suggest the effect this has on measured volume of bromine water.

A

Measured volume would be greater
Level in burette falls as tap is filled before any liquid is delivered

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17
Q

But-1-ene reacts with a reagent of the form HY to form a saturated compound. Suggest a reagent of the form HY which reacts with but-1-ene

A

HBr or HCl or H2SO4

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18
Q

Ethene can produce ethanol from ethene by direct hydration or from glucose by fermentation. State conditions for hydration reaction.

A

Conditions needed :
High temp and high pressure
SiO2 coated in phosphoric acid which acts as a catalyst.

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19
Q

How to know if direct hydration is occuring. State reagents and conditions of direct hydration

A

When water reacts with alkenes to turn into alcohols.
Reagents : H2O
Conditions : Concenrated H3PO4 catalyst

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20
Q

Reagents and observations or propane and propene

A

Reagent : Shake with Br2
Observation of propane : stays orange/red/yellow / no observed change / no visible change
Observation of propene : Decolourised / goes colourless / orange to colourless

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21
Q

Reagents and observations of aqeuous silver nitrate and aqeous sodium nitrate

A

Reagent : any soluble acid including hydrochloric acid
Observation of aqeous silver nitrate : White precipitate forms
Observation of aqeous sodium nitrate : remains colourless or no observed change

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22
Q

Reagents and observations of aqeous magnesium chloride and aqeous barium chloride

A

Reagent : Any soluble sulfate including (dilute or aqeous) sulfuric acid
Observation of aqeous magnesium chloride : Remains colourless or no observed change
Observation of aqeous barium chloride : white precipitate forms / white solid forms

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23
Q

Chemical tests can be used to distinguish between seperate samples of pent-2-ene and cyclopentane. Identify a suitable reagent for the test

A

Reagent : Br2
Observation with pent-2-ene : decolourised / goes colourless
Observation of cyclopentane : Remains orange / no observable change

24
Q

Write an equation for reaction of concentrated sulfuric aid reacting with hydrigen bromide to form bromine as one of the products.

A

2HBr + H2SO4 -> Br2 + SO2 + 2H2O

25
Q

Deduce type of reaction of (CH3)2C(OSO2OH)CH3 + H20 -> (CH3)2C(OH)CH3 + H2SO4

A

Hydrolysis

26
Q

Formula of but-2-ennitrile

A

H3CC=CHCN

27
Q

give a reagent and conditions for the reaction CH3CH2Br -> CH3CH2OH. Also state one reason why this method is not used in industry to make ethanol

A

Reagent : NaOH or KOH
warm and aqeous solution/ water
Reaction : Yield is very slow/ rate of reactions is slow /Bromoethane is is expensive / Bromoethane has to be manufactured

28
Q

Identify the type of reation, a suitable catalyst and give two conditions necessary to produce a high yield of ethanol
H2C=CH2 -> CH3CH2OH

A

Catalyst: Concentrated H2SO4
Type of reaction : electrophilic addition
Conditions : excess water / recycle ethene / remove ethanol as it forms

29
Q

Name mechanism for when 2-bromopentane reacts with ethanolic KOH

A

elimination

30
Q

Propene reacts with hydrogen bromide. Draw structure of intermediate that leads to formation of major in this reaction

A

H3CCH+CH3

31
Q

2-bromopropane reacts with sodium hydroxide. It can undergo elimination and nucleophulic substitution. State what is produced in each mechanism

A

Nucleophilic substitution : Pentan-2-ol + Br^-
Elimination : Propene + Br^- + H2O

32
Q

State reagent and conditions for turning 2-bromopropane into propene

A

Reagent : NaOH
Conditions : ehtanolic or alcoholic solvent

33
Q

Name class of alcohols to which propan-2-ol belongs in

A

Secondary

34
Q

State reagents and conditions for reaction H3CC(CH3)OSO3HCH2CH3 into CH3C(CH3)OHCH2CH3

A

Reagent : H2O
Conditions : heat warm or boil or reflux

35
Q

Unsaturated vegetabes oils are hardened. State reagents and conditions.

A

Reagents : H2
Conditions : Ni (catalyst)

36
Q

Soft and hard margarines are obtained from the same vegtable oil. How do the structure of these two differ and melting point

A

Hard margarine has higher boiling point as soft maargarine has less hydrogenated or has more c=c double bonds or is more unsaturated tan the hard margarine

37
Q

An alcohol can react to produce two alkenes. Name type of reaction involved and identify the reagent

A

Elimination or dehydration
Reagent : H2S04

38
Q

What is meant by the term electrophile

A

Lone pair

39
Q

Explain what is meant by term addition

A

Reaction which increases number of covalent bonds to single bonds where two molecules form one molecule

40
Q

Explain why bromine, a non-polar molecule is able to react with propene

A

High electron density between the carbons

41
Q

The polymerisation of propene to form poly(propene) is an ipmortant industrial process. Name type of polymerisation

A

Addition

42
Q

State what you would observe if bromine water was added to poly(chloroethene)

A

No reaction because polymer is saturated

43
Q

Suggest why polychloroethene has a higher melting point than chloroethene

A

Polychloroethene has a bigger molecule. Polychloroehtne has stronger van de waals forces between molecules

44
Q

State a property of polychlororethene

A

It is flexible / bendy

45
Q

Golf balls recovered from lakes can be used again after being in water for several years. Explain why the golf balls do not biodegrade

A

Carbon carbon bonds are non polar / too strong
Carbon carbon bonds cannot be hydrolysed

46
Q

Conditions of elimination when reagent is NaOH

A

Ethanolic solvent

47
Q

Is this statement true or false about ethene
It burns in excess oxygen to produce carbon and water

A

True

48
Q

Explain why there is an attraction between c=c double bond and Br2

A

c=c bonds are areas of high eletron density
c=c double bond induces a dipole in Br2

49
Q

State mechanism (CH3)2C(OSO2OH)CH3 + H2O → (CH3)2C(OH)CH3 + H2SO4

A

Hydrolysis

50
Q

Name mechanism and product of reaction between cyclohexene and Br2

A

Mechanism : electrophilic addition
Product : 1,2 - dibromocyclohexane

51
Q

State condition and reagent : CH3C(OSO3H)(CH3)CH2CH3 -> CH3C(OH)(CH3)CH2CH3

A

Reagents : H20
Conditions : Heat

52
Q

State reagent and conditions for Nucleophilic substitution when NH3 is used

A

Excess NH3

53
Q

State reagent and conditions for free radical substitution when bromine is being used

A

Br2
UV light

54
Q

Name mechanism, reagents, and conditions for when CH3CH2CH2OH turns into C3H6

A

Mechanism : elimination
Reagents : Hot concentration of H2SO4

55
Q

Name mechanism and reagent for reaction of propene into 2-bromopropane

A

Mechanism : electrophilic addition
Reagents : HBr

56
Q

Name mechanism and reagents of reaction of 2-bromopropane into 2-methylpropanenitrile

A

Mechanism : nucleophilic substitution
Reagent : KCN
Conditions : aqueous solution and water

57
Q

Name CH3CH(CN)CH3

A

2-methylpropanenitrile

Chemistry 2.0 (9 decks)

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