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My Chemistry > Hydrocarbons in organic > Flashcards

Hydrocarbons in organic Flashcards

1
Q

Why does the chain length of alkanes increase the boiling point?

A

More points of contact so more London forces induced, therefore more energy required to overcome

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2
Q

Why does boiling points of alkanes decrease with branching?

A

Less surface area as packing is further, resulting in weaker and less London forces

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3
Q

What is the overall equation for monosubstitution giving chloromethane?

A

CH4 + Cl2 = CH3Cl + HCl

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4
Q

What is the equation for free radical substitution of methane and chlorine?

A

CH4 + Cl2 = C2H6 + HCl + CH3Cl

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5
Q

What is the initiation step in free radical substitution of methane and chlorine?

A

Absorption of UV causes photodissociation of Cl2 and homolytic fission occurs

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6
Q

What are the propagation steps that occur in free radical substitution of methane and chlorine?

A

1: Chlorine radical reacts with methane molecule to make HCl and methane free radical (.CH3)
2: Methyl radical reacts with chlorine molecule to produce chloromethane and another chlorine radical

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7
Q

What are the termination steps that occur in free radical substitution of methane and chlorine?

A

Any two free radicals react to form either a chlorine molecule, ethane or chloromethane

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8
Q

What are the three steps in free radical substitution mechanism?

A

Initiation step, propagation steps and termination steps

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9
Q

Why do alkenes undergo addition reactions?

A

Due to the relatively low bond enthalpy of the pi bond

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10
Q

What is hydrogenation?

A

Addition of hydrogen to an alkene

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11
Q

What is the reagent and conditions for hydrogenation?

A

H2, Ni catalyst and 150C

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12
Q

What is the equation for hydrogenation of propene?

A

Propene + hydrogen molecule = propane

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13
Q

What is halogenation?

A

Addition of halogens to alkenes

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14
Q

What is the reagent and conditions for halogenation?

A

X2, RT

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15
Q

What happens when bromine is used in halogenation?

A

When an alkene is bubbled through a solution of bromine in an inert organic solvent, the brown bromine solution is rapidly decolourised

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16
Q

How is the use of bromine in halogenation beneficial?

A

Acts as a test for unsaturation

17
Q

What is the halogenation equation for propene with bromine?

A

Propene + bromine molecule = 1,2- bromopropane

18
Q

What are the reagents and conditions for addition hydrogen halide to an alkene?

A

HX, RT

19
Q

What is the equation for ethane + hydrogen chloride?

A

Chloroethane

20
Q

How can alkenes be used to make alcohols?

A

Addition of steam using an acid catalyst

21
Q

What is the reagent and conditions for making alcohols from alkenes?

A

H2O, 600K 6mPa and H3PO4 catalyst

22
Q

What’s the equation for making an alcohol from propene?

A

Propene + steam = propan-1-ol or propan-2-ol

23
Q

Why can alkenes for polymers?

A

Because they are unsaturated

24
Q

What are the conditions for alkene polymerisation?

A

High temperatures and pressures or in the presence of a catalyst

25
Q

What are the advantages of combustion for energy production of waste polymers?

A

Difficult to recycle and produces heat/generate electricity

26
Q

What are the disadvantages of the combustion for energy production of waste polymers?

A

Produces CO2

27
Q

What are the advantages of using waste polymers as an organic feedstock for the production of plastics and other organic chemicals?

A

Can be used to recycle unsorted + unwashed polymers and is used for making new materials

28
Q

What are the disadvantages of using waste polymers as an organic feedstock for the production of plastics and other organic chemicals?

A

Requires a lot of energy

29
Q

What are the advantages of using waste polymers for the removal of toxic waste products?

A

Use alkali scrubbers to prevent HCl being released and use of solvent to dissolve and precipitate new PVC

30
Q

What are the disadvantages of using waste polymers for the removal of toxic waste products?

A

Expensive

31
Q

What is an electrophile?

A

An electron pair acceptor

32
Q

What is a carbocation?

A

Carbonium ion (C+)

33
Q

What type of reaction does hydrogen molecules and hydrogen halides undergo when they react with alkenes?

A

Heterolytic fission

34
Q

What do curly arrows on diagrams do?

A

Show the movement of a pair of electrons; showing either heterolytic fission or formation of a covalent bond from a lone pair of electrons

35
Q

How do asymmetrical alkenes give a mixture of products?

A

They have primary, secondary and tertiary carbocations for the halogen to bond to

36
Q

How is the attachment of halogens determined between the primary secondary and tertiary carbocation?

A

The route with the most stable carbocation will lead to the major product e.g. tertiary> secondary> primary

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