Alkenes Flashcards

1
Q

what general formula does alkenes fit?

A

alkenes are hydrocarbons that fit the general formula CnH2n

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2
Q

how do alkenes work?

A

they work like alkanes, except that they have one C=C double-bond in their carbon change

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3
Q

what is the formula for ethene?

A

C2H4

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4
Q

how many ‘n’ does ethene have?

A

2

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5
Q

what is the formula for propene?

A

C3H6

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6
Q

how many ‘n’ does propene have?

A

3

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7
Q

what is the formula for butene?

A

C4H8

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8
Q

how many ‘n’ does butene have?

A

4

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9
Q

what is the formula for pentene?

A

C5H10

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10
Q

how many ‘n’ does pentene have?

A

5

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11
Q

how do we know alkenes contain the C=C double bond?

A

the names of alkenes end in ‘-ene’

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12
Q

how is the double bond written in a structural formula?

A

’=’
e.g. CH2=CHCH2CH3

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13
Q

what are alkenes?

A

alkenes are a homologous series of organic molecules, like alkanes but slightly different - however they are still a family of molecules

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14
Q

what three key features do alkenes?

A
  • similar chemical reactions
  • trends in physical properties (e.g. boiling points, viscosity or colour)
  • the same general formula
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15
Q

what are isomers?

A
  • like alkanes, alkenes also have isomers
  • but unlike alkanes, their isomers can differ in more than one way
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16
Q

how can isomers be different?

A
  • different branching of the carbon chain
  • different positions of the C=C in the carbon chain
17
Q

why are alkenes referred to as unsaturated?

A

because they have a C=C double bond

18
Q

why are alkenes referred to as saturated?

A

because they don’t have a C=C double bond

19
Q

can alkenes combust in oxygen?

A

yes - to release energy (they can also incompletely combust)

20
Q

what happens when alkenes react with bromine?

A

they break the C=C bond and add the bromine atoms in

21
Q

what type of reaction is alkenes reacting with bromine?

A

an addition reaction - because you are adding the bromine atoms into the alkene

22
Q

can alkene and bromine reaction happen without UV light?

A

yes - because alkenes are more reactive than alkanes

23
Q

what state does bromine need to be in to react with alkenes?

A

with pure bromine liquid or bromine water (orange)

24
Q

what colour does the mixture of bromine and alkenes turn?

A

from orange to colourless - because bromine is used up in the reaction

25
Q

what is bromine and alkene reaction used to test for?

A

the C=C in unsaturated compounds