Alkenes Flashcards

1
Q

Are alkenes saturated or unsaturated hydrocarbons?

A

unsaturated

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2
Q

What is meant by the term unsaturated hydrocarbon?

A

They are made with carbon and hydrogen only, and have at least one carbon-carbon double bond. This means that they are not bonded to the maximum number of hydrogen atoms

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3
Q

Why are alkenes more reactive than alkanes?

A

They are more reactive due to the carbon-carbon double bond which provides an electron rich area (high electron density) between the two carbon atoms (they are more vulnerable to attack from a electrophile).

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4
Q

What is the general formula for an alkene?

A

CNH2N

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5
Q

Why cant alkenes rotate about the carbon-carboon double bond?

A

On each carbon atom there is a p orbital. As these carbon atoms create a double bond the two p orbitals overlap forming an orbital (pi orbital) with a cloud of electron density above and below the double bond, which prohibits it from rotating.

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6
Q

draw the structures of the p orbitals turning into a pi orbital between the double bonds of an alkene

A

Check page 217

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7
Q

What are the names of the two types of isomers that involve the double bond?

A

position isomers

geometrical isomers

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8
Q

What are positional isomers?

A

They are isomers where the double bond is places in different positions along the hydrocarbon chain

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9
Q

What are geometrical isomers?

A

A form of stereoisomer

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10
Q

What is a stereoisomer?

A

They have the same structural formula but the bonds are arranged differently in space (they occur only around the c-c double bond)

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11
Q

What is another name for geometrical isomers?

A

E-Z isomerism

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12
Q

What is the name of the type of isomer with the highest groups on the same side of the c-c double bond

A

z isomer

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13
Q

What is the name of the type of isomer with the highest groups on the opposite side of the c-c double bond

A

E isomer

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14
Q

What did E-Z isomerism used to be called?

A

cis-trans isomerism

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15
Q

How would you know weather an isomer was an E or a Z?

A

weather or not the atoms with the largest atomic number are on the same side of the c-c double bond.

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16
Q

What are the only intermolecular forces that act between alkene molecules?

A

van der Waals forces

17
Q

How are the properties of alkenes similar to that of alkanes?

A

They are not soluble in water

Their melting and boiling points increase as the chain length increases

18
Q

What is the bond enthalpy for a c-c single bond?

A

347 kJ mol-1

19
Q

What is the bond enthalpy for a c-c single bond?

A

612 kJ mol-1

20
Q

What is the definition of an electrophile?

A

They are an electron pair acceptors