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Organic Chemistry > Alkenes > Flashcards

Alkenes Flashcards

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1
Q

What is the general formula for an alkene?

A

CnH2n

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2
Q

What other thing has the general formula CnH2n

A

Cycloalkanes

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3
Q

What makes alkenes very reactive?

A

They are unsaturated compounds, with regions of high electron density

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4
Q

What is the hybridisation of carbon in alkenes?

A

sp2 hybridised

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5
Q

What is a symmetrical alkene?

A

This is an alkene with an equal number of carbons on either side of the C=C bond

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6
Q

What is an asymmetrical alkene?

A

This is an alkene with an unequal number of carbons on either side of the C=C bond

This gives room for a mixture of products to be formed in chemical reactions

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7
Q

What reactions do alkenes undergo?

A
  1. Oxidation
  2. Electrophilic addition
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8
Q

What reagents commonly react with alkenes?

A

Halogen molecules or hydrogen halides

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9
Q

What property of hydrogen halides makes them act as electrophiles?

A

The electronegativity difference in the H-X bond, giving the H a δ+ charge

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10
Q

How are the neutral halogen molecules made polar?

A

A dipole is induced when the halogen molecule approaches the electron rich C=C bond.

e- repulsion occurs, making the halide atom closer to the C=C bond have a δ+ charge

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11
Q

Do alkenes decolourise bromine water?

A

Yes

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12
Q

What rule is typically followed when determining the major product in the reaction of an alkene with a hydrogen halide?

A

Markovnikov’s rule

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13
Q

What does Markovnikov’s rule basically imply?

A

The most stable carbocation is formed in the intermediate step

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14
Q

State Markovnikov’s rule

as applies to the reaxn. with hydrogen halides

A

When an asymmetrical alkene reacts with a hydrogen halide, the hydrogen atom bonds with the carbon that has** the higher number** of carbon atoms

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15
Q

What bond is broken when alkenes react?

A

The π bond; the second bond of the C=C double bond

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16
Q

What is a polymer?

A

A large molecular compound made of repeating units of monomers

17
Q

What is a monomer?

A

A small molecular unit which combines with other (like or unlike) monomers to form a large molecule

18
Q

What quality differentiates a polymer from a monomer?

A

Polymers are saturated and monomers are not

19
Q

While monomers are typically volatile liquids or gases, polymers are…?

A

Solids

The Van der Waal’s forces are stronger in polymers due to the large molecular structure

20
Q

What are the two types of polymerisation you know?

A
  1. Addition polymerisation
  2. Condensation polymerisation
21
Q

How does condensation polymerisation differ from addition polymerisation?

A

There is the elimination of a small molecule in condensation polymerisation

Hence two products are formed as opposed to one in the latter

22
Q

What is peculiar about a polymer

A

It is formed from repeating units of something

23
Q

True or False?

Addition polymerisation occurs in alkenes only

A

True

24
Q

In what type of polymerisation do the monomers have to be the same?

A

Addition polymerisation

25
Q

In what type of polymerisation can the monomers afford to be different?

A

Condensation polymerisation

26
Q

What are the reaction conditions (reagents, catalyst, reacting system)

for the addition polymerisation of alkenes?

A
  1. REAGENTS: The monomer (containg the C=C bond)
  2. CATALYST: An organic peroxide
  3. REACTING SYSTEM CONDITIONS: High temperature and pressure
27
Q

Why is an organic peroxide used as a catalyst?

for the addition polymerisation of alkenes?

A

They readily break up to form free radicals

These free radicals are very reactive and form a bond with one carbon, breaking the π bond and forming another electrophile

28
Q

Yes or No

Is there free rotation about the C=C double bond?

A

No

29
Q

What two compounds can be found in bromine water?

A

HBr and HOBr

30
Q
A
31
Q

What catalyses the hydration of an alkene to an alkane

A

Finely-divided Iron or Nickel

32
Q

What can be physically observed when an alkene is mixed with cold dilute acidified KMnO4?

A

The solution turns from purple to colourless

33
Q

What is formed when an alkene is mixed with an aqueous solution of cold dilute acidified KMnO4?

A

A diol

Oxygen is added to either side of the C=C double bond when broken

34
Q

What is formed when an alkene is mixed with hot conc. acidified KMnO4?

A

An aldehyde/carboxylic acid/ketone

Oxygen is added to either side of the C=C double bond when broken

35
Q

Why is there a difference in the products depending on the concentration and temperature of the acidified KMnO4?

A

A hot and concentrated mixture present much harsher reaction conditions

Organic Chemistry (7 decks)

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