Exam 2 - Wittig Reaction, HWE Reaction, and Ylides

Question 1

In the ___ ___, you add phosphonate and NaOCH3 (base) to a ketone/aldehyde in order to create an attached E alkene.

Answer 1

HWE Reaction

Question 2

Strong bases for the conversion of phosphonium salt to an ylide include:

Answer 2

NaH, NaNH2, nBuLi, R-Li

Question 3

You can make a phosphonium ylide by reacting ___ with ___, to make a phosphonium salt. Then, add a strong base such as ___ or ___ to the phosphonium salt, in order to make the phosphonium ylide.

Answer 3

triphenylphosphine reacts with CH3-X (Where X = I,Br,Cl, etc.) to make the phosphonium salt. Then, add nBuLi or R-Li (strong base) to convert the phosphonium salt to a phosphonium ylide.

Question 4

In the HWE Reaction, you add phosphonate and NaOCH3 (base) to a ketone/aldehyde in order to create a(n) ___ ___ ___.

Answer 4

attached E alkene

Question 5

Stabilized ylides will produce ___ alkenes.

Answer 5

E alkenes (trans)

Question 6

*Note: You have to make the ___ for the HWE Reaction!

Answer 6

phosphonate

Question 7

*Note: If the Wittig reagent is an alkane larger than CH2, then the stereochemistry of the alkene will usually be ___.

Answer 7

Z

Question 8

In the HWE Reaction, you add ___ and ___ to a ketone/aldehyde in order to create an attached E alkene.

Answer 8

phosphonate and NaOCH3 (base)

Question 9

Stabilized ylide -> Ylide stabilized by ___ ___ ___.

Answer 9

nextdoor carbonyl group

Question 10

*___ your carbons to make sure you don’t lose any along the way!

Answer 10

Count Carbons

Question 11

In the Wittig Reaction, you react with a ___ ___ to convert a ketone/aldehyde to an alkene.

Answer 11

phosphonium ylide

Question 12

___ ylides will produce E alkenes (trans).

Answer 12

Stabilized ylides

Question 13

You need to make the phosphonate by adding either ___ or ___ to ___.

Answer 13

Add Br-Ester or Br-ketone to phosphite [P(OCH3)3] to make the phosphonate.

Question 14

*Note: You have to make the ___ ___ for the Wittig Reaction!

Answer 14

phosphonium ylide

Question 15

The E alkene may be ___ ___, but the intermediate can only change to E if the ylide is stabilized!

Answer 15

thermodynamically favored

Question 16

In the ___ ___, you react with a phosphonium ylide to convert a ketone/aldehyde to an alkene.

Answer 16

Wittig Reaction

Question 17

___ ___ -> Ylide stabilized by nextdoor carbonyl group.

Answer 17

stabilized ylide

Question 18

*Note: If the Wittig reagent is a(n) ___ larger than ___, then the stereochemistry of the alkene will usually be Z.

Answer 18

alkane larger than CH2

Question 19

___ ylides will produce Z alkenes (cis).

Answer 19

Unstabilized ylides

Question 20

A(n) ___ is when there are opposing charges on neighboring atoms, where one C does NOT have a full octet.

Answer 20

ylide

Question 21

You need to make a phosphonium salt by adding ___ and/or ___ ___ to triphenylphosphine. If you add a tertiary halide, you will do an E2 reaction instead.

Answer 21

primary and/or secondary halides

Question 22

In the Wittig Reaction, you react with a phosphonium ylide to convert a ketone/aldehyde to a(n) ___.

Answer 22

alkene

Question 23

Unstabilized ylides will produce ___ alkenes.

Answer 23

Z alkenes (cis)