Nucleophilicity of Alcohols

[suchgreatheights]

 

What would be a better nucleophile, ethanol or a bulkier alcohol? Such as isopropyl alcohol? Does size affect nucleophilicity? Thanks!

 

[khatereh]

Basity is different from nucleophilisity.

Bigger atoms are better nucleophile because they can polarize better than the small atoms because of that SH is better nucleophile than OH. but OH is better base because it is small and it can grab the protons more easier than SH.

 

Alcohols are not strong nuclephile. but if they want to act as nuclephile, the less bulky should be better for attacking to the electrophile.

if you mention the reaction that you are looking at, I might have ability to help more

[hypervalent_iodine]

Basity is different from nucleophilisity.

Bigger atoms are better nucleophile because they can polarize better than the small atoms because of that SH is better nucleophile than OH. but OH is better base because it is small and it can grab the protons more easier than SH.

 

Alcohols are not strong nuclephile. but if they want to act as nuclephile, the less bulky should be better for attacking to the electrophile.

if you mention the reaction that you are looking at, I might have ability to help more

 

Small note: the definitions of what is a base and what is a nucleophile do differ, but you should have also elaborated on what you meant by that, as it is a little confusing. Nucleophiles are Lewis bases by definition. So, all nucleophiles are in fact bases, but not all bases are nucleophiles. The distinction that you often see is that a nucleophilicity is all about reaction rate, whereas bases are all about the stability of the end product and by association, reaction equilibrium.

 

A simpler explanation comes from considering the fact that oxygen is more electronegative than sulphur, which means that it is less likely to want to donate its electrons to attack an electrophile. Atomic size comes into play due to the fact that you get better orbital overlap and because the nature of the orbitals makes them more susceptible to being polarized, which increases nucleophilicity. This in turn makes reactions such as the S_N2 reaction occur via a transition state that is lower in energy. There is also the hardness of the nucleophile to consider. This isn't really related to the OP, though.

 

The size of the molecule as a whole is more or less how you've described. I'm not going to elaborate, however, as SFN has a policy of not providing answers to homework questions. In future, if you could please provide less in the way of straight up answers to these sorts of questions and more in the way of guidance and help towards getting the answer, it would be appreciated. That way the student actually learns something.

[khatereh]

OK sure!!!

 

 

 

 

Small note: the definitions of what is a base and what is a nucleophile do differ, but you should have also elaborated on what you meant by that, as it is a little confusing. Nucleophiles are Lewis bases by definition. So, all nucleophiles are in fact bases, but not all bases are nucleophiles. The distinction that you often see is that a nucleophilicity is all about reaction rate, whereas bases are all about the stability of the end product and by association, reaction equilibrium.

 

A simpler explanation comes from considering the fact that oxygen is more electronegative than sulphur, which means that it is less likely to want to donate its electrons to attack an electrophile. Atomic size comes into play due to the fact that you get better orbital overlap and because the nature of the orbitals makes them more susceptible to being polarized, which increases nucleophilicity. This in turn makes reactions such as the S_N2 reaction occur via a transition state that is lower in energy. There is also the hardness of the nucleophile to consider. This isn't really related to the OP, though.

 

The size of the molecule as a whole is more or less how you've described. I'm not going to elaborate, however, as SFN has a policy of not providing answers to homework questions. In future, if you could please provide less in the way of straight up answers to these sorts of questions and more in the way of guidance and help towards getting the answer, it would be appreciated. That way the student actually learns something.