Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
9 Cards in this Set
- Front
- Back
An Aldehyde or ketone is converted into an alkene by means of the
|
Wittig rxn
|
|
In the Wittig rxn, a phosphorus ylide, R2C-P(C6H5)3) adds to an aldehyde or ketone to yield ..
|
a dipolar intermediate called a betaine
|
|
The betaine intermediate is not isolated, rather, it
|
spontaneously decomposes through a four membered ring to yield alkene and triphenylphosphine oxide
(Ph)3=O |
|
The net result of the betaine intermediate is the ...
|
replacement of the carbonyl oxygen atom by the R2C= group originally bonded to phosphorus
|
|
The phosphorus ylides necessary for Wittig rxn are easily prepared by?
|
Sn2 rxn of primary(and sometimes secondary) alkyl halides with triphenylphosphine, followed by treatment with base
|
|
Triphenylphine, (Ph)3P, is a good nucleophile in an Sn2 rxn, and yields of
|
the resultant alkyltriphenylphosphonium salts are high
- Cuz of the positive charge on the phosphorus, the hydrogen on the neighboring carbon is weakly acidic and can be removed by a base such as butyllithium (BuLi) to generate the neutral ylide |
|
The Wittig rxn is extremely general in its applications, and a great many mono-, di-, and tri- substituted alkenes can be ...
|
prepared from the appropriate combo of phosphorane and aldehyde or ketone
|
|
The real value of the Wittig rxn is that it yields a ?
|
pure alkene of known structure.
|
|
The C=C bond of the Wittig Rxn in the product is always...
|
exactly where the C=O group was in the reactant, and no alkene isomers (except E,Z isomers) are formed
|