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Flashcards in Alkenes Deck (29):
1

How can you make an alkene from an alkyne

1) Lindlars catalyst and H2
2) NH3/ Na
3) H2 and pt goes all the way to alkane

2

What sort of addition is lindlars

Syn

3

What sort of addition is NH3 (low) / Na

Radical mechanism
Anti

4

Define stereoselective

The reaction pathway has a choice

5

Describe an E1 mechanism

2 steps
Dilute tertiary
Stereoselective
Eclipsed conformer is fastest reaction as steric strain is removed

6

Why is E1 stereoselective

The carbon bond can rotate freely

7

Describe an E2 mechanism

1 step
Favours primary and concentrated
Stereospecific
Favours staggered

8

Why is E2 stereospecific

The elimination can only proceed via anti periplanar conformation

9

Define regioselectivity

The reaction has a choice of products but one is favoured over the other

10

Is E1 regio selective or specific

Regioselective - the Saytzeff rule states that the most highly substituted Alkene is formed

11

Is E2 regio selective or specific

Regioselective - follows saytzeff unless a large bulky base is used then it follows Hofmann - least sub alkene favoured

12

What is a large bulky base

Potassium tert butoxide

13

In a cyclic ring elimination what conformer is required

1,3 diaxial

14

How can you make an alkene from an alcohol

Acid catalyst

15

What are elimination reactions in competition with

Sub because the base can act as a nucleophile

16

What does the Wittig reaction use

Aldehyde or ketone and phosphorane

17

What is the Wittig reactions selectivity and specificity

Regiospesific and stereoselective

18

How can you produce phosphorane

PPH3 + CH3Br -> salt BuLi
Or
Alpha halo Ester and NaOH

19

What determines the stereoselectivity of Wittig

Electron withdrawing gives E

20

What does the Julia Olefination use

Phenylsulfone and ketone
Acetic anhydride
Na/Hg

21

What is the specificity and selectivity of the Julia reaction

Regiospesific and stereoselective

22

What does the Peterson reaction use

Silylcarbanions

23

What is produced under acidic conditions in the Peterson.

Trans alkene

24

What is produced under basic in Peterson

Cis

25

What does the McMurry coupling use

Ti radicals

26

What is the regio of McMurry

Regiospesific

27

Which step in alcohol elimination is reversible

The first

28

What conditions we required for basic Peterson

KF3

29

What conditions are required for the acidic Peterson

BF3