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Chemistry Organic 1 > Alkenes (Chapter 14) > Flashcards

Alkenes (Chapter 14) Flashcards

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1
Q

What are alkenes?

A

Unsaturated hydrocarbons (double bond)

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2
Q

Describe the bonding in alkenes

A

Involves a double covalent bond (centre of high electron density)

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3
Q

What is used to test if a hydrocarbon is saturated?

A

Bromine water which turns colourless (as double bond is broken and bromine substituted onto alkene.)

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4
Q

What is the formula for alkenes?

A

CnH2n

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5
Q

Why do alkenes have stereoisomers?

A

The overlapping pi bond restricts rotation around the double bond.

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6
Q

Define electrophile

A

An electron pair acceptor.

Has partial or full charge so is electron deficient

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7
Q

Compare the properties of E vs Z isomers

A

E isomers can pack together more easily, so have stronger intermolecular forces and therefore tend to have higher melting points.

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8
Q

What reaction forms haloalkenes?

A

Electrophilic addition reactions

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9
Q

What is a primary carbon cation?

A

Positively charged carbon on the end of a hydrocarbon

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10
Q

What is a secondary carbon cation?

A

Positive charge carbon within hydrocarbon chain (bonded to two other carbons).

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11
Q

What is a tertiary carbon cation?

A

Positively charged carbon in a carbon chain with alkyl group (bonded to 3 other carbons).

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12
Q

Order the carbon cations from least to most stable

A

Primary - least
Secondary
Tertiary - most

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13
Q

How are priority groups assigned?

A

By their atomic number

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14
Q

What forces are between alkenes?

A

Weak Van-der-Waals forces

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15
Q

What is the pattern for boiling points in alkenes?

A

The more carbons then the higher the boiling point.

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16
Q

Describe the stages in an an electrophilic addition reaction

A

1) The electrophile is attracted to the double bond.
2) Electrophiles are positively charged and accept a pair of electrons from the double bond. (May be a positive ion or have a positively charged area)
3) A positively charged carbon (cation) is formed.
4) A negatively charged ion forms with the carbocation.

17
Q

What is meant by heterolytic bond breaking?

A

When a covalent bond breaks and both electrons go to one of the atoms involved and none to the other. This results in a positive and negative ions being formed.

18
Q

What is a positive inductive effect?

A

The idea that alkyl groups have a tendency to release electrons.

19
Q

What is produced when water is reacted with an alkene?

A

Alcohol

20
Q

How is a polymer drawn?

A

Square brackets around the monomer with broken double bond and n next to brackets or number of repeating units.

21
Q

What are plasticisers?

A

Small molecules that get between the polymer chains forcing them apart and allowing them to slide across each each other.

22
Q

How is low density (poly)ethene made?

A

Polymerising ethene at high pressure and high temperature via free radical mechanism.

23
Q

Describe the properties of low density poly(ethene)

A

Do not pack together and are quite flexible and stretch easily.

24
Q

What are some uses for low density poly(ethene)?

A

Packaging (e.g. plastic bags), sheeting and electrical cables.

25
Q

How is high density (poly)ethene made?

A

Slightly higher temperature and pressure and than room temperature and use a Ziegler-Natta catalyst.

26
Q

Describe the properties for high density

A

Few branches (about 1/200 carbons). Can pack together well so the density of plastic greater and its melting point is higher.

27
Q

What are some uses for high density poly(ethene)?

A

Milk crates and bottles

28
Q

What is mechanical recycling?

A

Melting and remoulding poly(ethene)

29
Q

What is feedstock recycling?

A

Heating poly(ethene) to a temperature that breaks the bonds and making new plastics.

30
Q

Describe the steps of mechanical recycling

A

1) Different plastics are separated
2) Plastics washed and ground into pellets.
3) Melted and remoulded
e. g. drinks bottles made into fleece clothing

31
Q

What is a problem with feedstock recycling?

A

It can only be carried out a limited number of times because at each heating some of the chains break and become shorter therefore degrading the plastic’s properties.

32
Q

What is a stereoisomer?

A

Compounds/molecules with the same structural formula but with atoms/bonds/groups arranged differently in space

33
Q

What is an addition reaction?

A

Reaction which increases number of substituents or converts a double bond to single bond.

34
Q

What is poly(chloroethene) used for?

A

Rigid plastic as strong intermolecular bonding but its plasticiser is can be used as PVC as intermolecular bonds are broken.

35
Q

What are the properties of poly(chloroethene)?

A

Waterproof, electrical insulator and doesn’t react with acid.

Chemistry Organic 1 (6 decks)

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