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Flashcards in a level Alkenes Deck (18)
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1
Q

what is the nature of the double bond?

A

a sigma bond surrounded by a pi bond

2
Q

what is a pi bond?

A

the overlap of two p orbitals

3
Q

what shape are alkenes and why?

A

trigonal planar
3 regions of e- density around each c atom
all in the same plane

4
Q

what are stereoisomers?

A

have the same structural formula but a different arrangement of atoms in space

5
Q

what conditions are required for E/Z isomerism?

A

a c=c double bond

different groups attached to each c of the double bond

6
Q

what is cis-trans isomerism?

A

where one of the groups on each carbon is hydrogen

7
Q

what is the Cahn-Inglod-Prelog rule?

A

what distinguishes E/Z isomers

8
Q

how do you determine an atoms priority?

A

highest atomic no.

9
Q

why are alkenes relatively reactive?

A

the pi bond breaks easily

10
Q

why does the pi bond break easily?

A

bond enthalpy is weaker

11
Q

what addition reactions do alkenes undergo?

A

hydrogenation
halogenation
hydrogen halides
steam

12
Q

what conditions for hydrogenation?

A

423K and nickel catalyst

13
Q

what conditions for halogenation?

A

none but adding bromine water tests for unsaturation

14
Q

what conditions for the addition of hydrogen halides?

A

room temperature

15
Q

what conditions for hydration?

A

phosphoric acid catalyst

16
Q

why does electrophilic addition occur?

A

the double bond is an area of high e- density

this attracts electrophiles

17
Q

what is an electrophile?

A

a small molecule that accepts an electron pair and is added across the double bond

18
Q

what is the electrophilic mechanism?

A

the positive dipole is attra