Alkenes Flashcards

1
Q

What is an alkene

A

A hydrocarbon that is unsaturated ( has one or more double bond )

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2
Q

What are the two types of bond

A

Sigma and Pi

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3
Q

what is a sigma bond

A

The overlap of two s orbitals

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4
Q

What is a pi bond

A

The sideways overlap of P orbitals

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5
Q

What is stronger a sigma or pi bond

A

Sigma

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6
Q

Why are alkenes more reactive than alkanes

A

Alkanes only have a sigma bond whereas alkenes have pi bonds which are much weaker and therefore easier to break

The double bond has a high e- density and therefore it is more likely to be attacked by nucleophiles

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7
Q

Can double bonds rotate

A

absaloutly not

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8
Q

what his sterioisomerism

A

Compounds with the same structural formula but a different arrangement in space

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9
Q

What is z isomerism

A

When. the dominant groups are on Z- same ziddeee

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10
Q

What is E isomerism

A

When the dominant group are on different sides

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11
Q

How do you decide priority for Z/E isomerism

A

go through the groups and find the first difference, the one with the highest Atomic number has priority

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12
Q

What is cis/ trans isomerism

A

when there are 2 of the same groups around a double bond. Cis means they are on the same side. Trans mean they are on different sides

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13
Q

What is electrophilic addition

A

When the double bond b and in an alkene opens up and atoms are added to the carbon atom

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14
Q

What is an electrophile

A

an electron pair acceptor

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15
Q

What are the conditions required to add hydrogen to an alkene

A

Nickle catalyst 150 degrees

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16
Q

How do you react an alkene with halogens to form dihaloalkanes

A

The double bonds repel electrons in Br2 making it polar (add delta +/-

Hetrolytic bond fission occurs in Br2 (curly arrow )

The double bond opens up and the delta + Br is added on and a positive carbocation is formed (put a + on the carbon that hasn’t been bonded). Also draw the Br- radical that has formed with 2 delocalised e-

Draw an arrow from the Br radical to the + carbocation and join em

17
Q

What conditions are needed for steam hydration of alkenes

A

300 degrees steam and 60-70 atm of pressure

18
Q

Addition of alkenes with hydrogen halides

A

Her splits and then its the same

19
Q

markonikoffs rule

A

The major product from addition an unsymmetrical compound with an unsymmetrical alkene I the one where the positiver result of bond fission is added to the carbon with the most hydrogens attached

20
Q
A