Hey Marya, do you mean the ylide? We need a good nucleophile to attack the carbonyl carbon in which case. It is the nucleophillic qualities rather than basicity which is important.
@@ChadsPrep No Sir.i am talking when we form a ylide from alkyltriphosphonium salt then we use strong base to remove hydrogen from adjacent to phosphorus.
Maryam, note that the ylide is somewhat carbanion-like (look at one of its resonance structures). Carbanions are super strong bases themselves and it will require an even stronger base (BuLi) to deprotonate and form the ylide. If you look at butyl lithium it is even more carbanion-like which is why it is a stronger base than the ylide which is why it works here. For reference, the pKa of the conjugate acid of the ylide is ~35 whereas the pKa of butane (which is the conjugate acid of BuLi) is ~50. Hope this helps!
@@ChadsPrep Hi Mr Chad. No you didn't say that in the video. But I do always solve many organic questions and I've seen that carboxylic acid has been converted into esters during alkylation, wittig reaction and many other things. I'm not sure why?
Many strong nucleophiles are also strong bases and would be protonated in a protic solvent (think Grignard) let alone if you had an actual acid present. In the case of a carboxylic acid, you can convert it into an ester before reaction with certain nucleophiles and then convert it back to an acid afterwards. Otherwise, you might/would protonate the nucleophile at which point it would no longer be as strong a nucleophile (or even a nucleophile at all). Hope this helps!
Hello fakhrul! You would think so, and if instead of phosphorous you put any element from the second period (like Nitrogen) with 3 phenyl groups attached and it would struggle to do backside attack. But the period 3 elements like phosphorus and sulfur have a much larger radius. For one this spreads out the phenyl groups farther from each other and farther from the side of the atom that will be attacking as a nucleophile. But it also results in them being much more polarizable. This means that their electron clouds are 'squishier' which allows them to change their shape to aid in nucleophilic attack. It might not be inuitive upon initial inspection but PPh3 is actually a pretty decent nucleophile. Hope this helps!
Thank you Chad for organizing these videos in a simple and easy way to understand.
You're welcome - glad they are helpful.
You're the oxygen to my phosphorus
😆😆😆
thank you Chad! you are the besttt!!
Thank YOU!
I love all your videos!!
Glad to hear it :) Happy studying!
Clearly presented😊
Thanks!
Hi Chad , did you do a lesson on kinetic acidity and thermodynamic acidity ? Also on the enolate and enol?
Why strong base is used in this reaction?
Hey Marya, do you mean the ylide? We need a good nucleophile to attack the carbonyl carbon in which case. It is the nucleophillic qualities rather than basicity which is important.
@@ChadsPrep No Sir.i am talking when we form a ylide from alkyltriphosphonium salt then we use strong base to remove hydrogen from adjacent to phosphorus.
Maryam, note that the ylide is somewhat carbanion-like (look at one of its resonance structures). Carbanions are super strong bases themselves and it will require an even stronger base (BuLi) to deprotonate and form the ylide. If you look at butyl lithium it is even more carbanion-like which is why it is a stronger base than the ylide which is why it works here. For reference, the pKa of the conjugate acid of the ylide is ~35 whereas the pKa of butane (which is the conjugate acid of BuLi) is ~50. Hope this helps!
@@ChadsPrep okay accept my big thanks.
Hi can I ask why carboxylic has to be converted into esters during alkylation and wittig reaction please? Thank you.
Hey - is this in reference to something said in the video?
@@ChadsPrep Hi Mr Chad. No you didn't say that in the video. But I do always solve many organic questions and I've seen that carboxylic acid has been converted into esters during alkylation, wittig reaction and many other things. I'm not sure why?
Many strong nucleophiles are also strong bases and would be protonated in a protic solvent (think Grignard) let alone if you had an actual acid present. In the case of a carboxylic acid, you can convert it into an ester before reaction with certain nucleophiles and then convert it back to an acid afterwards. Otherwise, you might/would protonate the nucleophile at which point it would no longer be as strong a nucleophile (or even a nucleophile at all). Hope this helps!
@@ChadsPrep cheers Chad
@@alaaammar4462 👍
PPh3 is so bulky ..how it performed sn2?
Hello fakhrul! You would think so, and if instead of phosphorous you put any element from the second period (like Nitrogen) with 3 phenyl groups attached and it would struggle to do backside attack. But the period 3 elements like phosphorus and sulfur have a much larger radius. For one this spreads out the phenyl groups farther from each other and farther from the side of the atom that will be attacking as a nucleophile. But it also results in them being much more polarizable. This means that their electron clouds are 'squishier' which allows them to change their shape to aid in nucleophilic attack. It might not be inuitive upon initial inspection but PPh3 is actually a pretty decent nucleophile. Hope this helps!
@@ChadsPrep u means like more polarizable?
@@fakhrulnawawi9681 exactly
Great
Thank you