Alkenes Flashcards

1
Q

What are alkenes?

A

Unsaturated hydrocarbons, meaning they contain at least one multiple bond between carbon atoms which in an alkene is a C to C double bond.

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2
Q

What is the general formula of alkenes?

A

CNH2N

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3
Q

What is a C to C double bond made up of?

A

-A sigma bond formed directly between two carbon atoms by the head-on single overlap of orbitals directly between bonding atoms
-A pie bond formed by the double sideways overlap of p-orbitals above and below the bonding atoms

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4
Q

What is the shape around each carbon?

A

Trigonal Planar, because there are three bonding regions of electron density around each of the carbon atoms that repel equally to each other creating a bond angle of 120.

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5
Q

What is the rotation around the C to C double bond?

A

Restricted.

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6
Q

What are sterioisomers?

A

Compounds with the same structural formula but with different arrangement of atoms in space.

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7
Q

What is the criteria for sterioisomers?

A

-must have C to C double bond as it cannot rotate
-each carbon must have two different groups attached to it

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8
Q

What is a Z isomer?

A

Where groups of higher priority are on the same side of the double bond.

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9
Q

What is an E isomer?

A

Where groups of higher priority are on diagonally opposite sides of the double bond.

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10
Q

Which atoms have the highest priority?

A

Those with higher atomic numbers.

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11
Q

What is the criteria for Cis-Trans sterioisomerism?

A

-must have C to C double bond as it cannot rotate
-each carbon must have two different groups attached
-two groups on the C to C double bond must be identical

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12
Q

What is a Trans isomer?

A

An E isomer.

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13
Q

What is a Cis isomer?

A

A Z isomer.

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14
Q

What reactions do alkenes undergo?

A

Electrophilic addition.

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15
Q

What are the conditions and reagents needed to turn an alkene into an alkane?

A

-Hydrogen gas
-Nickel catalyst, 150 degrees Celsius

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16
Q

What reagents/conditions are needed to turn an alkene into a dibromo alkane?

A

-room temperature
-Br2

17
Q

What reagents/conditions are needed to turn an alkene into a halide alkane?

A

-hydrogen halide
-room temperature

18
Q

What reagents/conditions are needed to turn an alkene into an alcohol?

A

-steam/H2O
-concentrated phosphoric acid, high temperature, high pressure

19
Q

What is an electoophile?

A

An electron pair acceptor.

20
Q

What is the most stable carbocation?

A

Tertiary.

21
Q

How do you decide which is the major/minor product in an electrophilic addition reaction with an unsymmetrical alkene e.g. propane?

A

The major product is the one which has the most most directly bonded alkyl groups attached
MINOR
-primary
-secondary
-tertiary
MAJOR

22
Q

What is addition polymerisation of alkenes?

A

Alkene monomers join together to from a long, saturated molecule called an addition polymer.

23
Q

What reagents/conditions are needed for addition polymerisation of an alkene?

A

-alkene monomer
-high temperature and pressure, catalyst

24
Q

What are problems with the disposal of addition polymers?

A

-non biodegradable
-incineration produces toxic gases e.g., HCl

25
Q

What are benefits of processing waste addition polymers?

A

-combustion for energy production
-removal of toxic waste products
-used in organic feedstock for the production of plastics and other organic chemicals

26
Q

What is the role of chemists in minimising environmental damage?

A

-develop biodegradable polymers
-develop photodegradable polymers(bonds that are weakened by light)
-use of an alkaline scrubber to neutralise HCl gas produced when incinerated