Why is bromide a better nucleophile than chloride?

[MedGrl@2022]

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Why is bromide a better nucleophile than chloride?

This refers to the question number #468 in 1001 in Orgo Chem Examkrackers.

 

[i5hina]

To simply answer your question, it's because bromide is bigger and more polarizable due to its size. Obviously, they have the same charge but the only difference is the size of the two. In addition, it's bulkier make up makes it a much favorable leaving group.

 

[Deadlifts]

Why is bromide a better nucleophile than chloride?

This refers to the question number #468 in 1001 in Orgo Chem Examkrackers.

http://forums.studentdoctor.net/showpost.php?p=2881966&postcount=4

 

[Greedo]

Reviving this question! #468 in 1001 in Orgo Chem Examkrackers says that Br- is a better nucleophile than Cl-, but #458 says that Br- is a better leaving group than Cl-. I get that Br- is bigger than Cl- and can therefore better stabilize the negative charge, making it a better leaving group. But wouldn't that also make it a worse nucleophile, because it can stabilize the negative charge better than Cl- and therefore has less reason than Cl- to react as a nucleophile?
How can something be both a better nucleophile AND a better leaving group?

 

[MedGrl@2022]

Reviving this question! #468 in 1001 in Orgo Chem Examkrackers says that Br- is a better nucleophile than Cl-, but #458 says that Br- is a better leaving group than Cl-. I get that Br- is bigger than Cl- and can therefore better stabilize the negative charge, making it a better leaving group. But wouldn't that also make it a worse nucleophile, because it can stabilize the negative charge better than Cl- and therefore has less reason than Cl- to react as a nucleophile?
How can something be both a better nucleophile AND a better leaving group?

I think your strong base with good nucleophile... like you said Br- is bigger than Cl- and can therefore better stabilize the negative charge, making it a better leaving group. I need to review this but I think its polarizability makes it a better nucleophile.

https://www.khanacademy.org/science...-sn2-e1-e2-jay/v/nucleophilicity-and-basicity

I need to review this as well. Let me know if you have more questions

 

[Greedo]

Great link, thanks!

 

[Yessi211]

To help with questions like this I think of nucleophiles as compounds willing to "give up their electrons" to others who need it (a.k.a electrophiles). Being that Cl is more electronegative than Br, Cl is less willing to give up those electrons as compared to Br.
Now as far as leaving groups go, because Br is the larger of the two, it can most successfully stabilize that negative charge. So while one concept has to do with the effective nuclear charge (nucleophilic strength), the other has to do with atom size (leaving group strength)
Hope that helps to distinguish the two!

 

[Endure]

Why is bromide a better nucleophile than chloride?

This refers to the question number #468 in 1001 in Orgo Chem Examkrackers.

Generally speaking, bromide is more polarizable than chloride, improving its ability to distribute electron density unevenly around the nucleus. However, the nucleophilicty of the halides is highly dependent on the solvent in which they are used. Flouride is a more potent nucleophile than bromide in a polar aprotic solvent because it is loosely bound to its solvent shell, whereas the opposite is true in polar protic solvents.

I doubt that last bit is useful, but it's good to keep in mind.