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Alkenes And Alkynes > Alkenes > Flashcards

Alkenes Flashcards

1
Q

How can you make an alkene from an alkyne

A

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

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2
Q

What sort of addition is lindlars

A

Syn

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3
Q

What sort of addition is NH3 (low) / Na

A

Radical mechanism

Anti

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4
Q

Define stereoselective

A

The reaction pathway has a choice

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5
Q

Describe an E1 mechanism

A

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

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6
Q

Why is E1 stereoselective

A

The carbon bond can rotate freely

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7
Q

Describe an E2 mechanism

A

1 step
Favours primary and concentrated
Stereospecific
Favours staggered

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8
Q

Why is E2 stereospecific

A

The elimination can only proceed via anti periplanar conformation

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9
Q

Define regioselectivity

A

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

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10
Q

Is E1 regio selective or specific

A

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

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11
Q

Is E2 regio selective or specific

A

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

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12
Q

What is a large bulky base

A

Potassium tert butoxide

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13
Q

In a cyclic ring elimination what conformer is required

A

1,3 diaxial

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14
Q

How can you make an alkene from an alcohol

A

Acid catalyst

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15
Q

What are elimination reactions in competition with

A

Sub because the base can act as a nucleophile

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16
Q

What does the Wittig reaction use

A

Aldehyde or ketone and phosphorane

17
Q

What is the Wittig reactions selectivity and specificity

A

Regiospesific and stereoselective

18
Q

How can you produce phosphorane

A

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

19
Q

What determines the stereoselectivity of Wittig

A

Electron withdrawing gives E

20
Q

What does the Julia Olefination use

A

Phenylsulfone and ketone
Acetic anhydride
Na/Hg

21
Q

What is the specificity and selectivity of the Julia reaction

A

Regiospesific and stereoselective

22
Q

What does the Peterson reaction use

A

Silylcarbanions

23
Q

What is produced under acidic conditions in the Peterson.

A

Trans alkene

24
Q

What is produced under basic in Peterson

A

Cis

25
Q

What does the McMurry coupling use

A

Ti radicals

26
Q

What is the regio of McMurry

A

Regiospesific

27
Q

Which step in alcohol elimination is reversible

A

The first

28
Q

What conditions we required for basic Peterson

A

KF3

29
Q

What conditions are required for the acidic Peterson

A

BF3

Alkenes And Alkynes (5 decks)

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