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How is neucliophilicity inversely proportional to basicity?

How is neucliophilicity inversely proportional to basicity?

Grade:12

4 Answers

ABIJAY BHAT
26 Points
5 years ago
The empirical concepts of basicity and nucleophilicity are related but not strictly proportional. Hence, the aim of this study is to help in elucidating the range where both concepts are directly proportional. To do this, the relationship between a recently introduced nucleophilicity index and the proton affinity (PA) of several families of bases has been studied. A good correlation between the PA and the nucleophilicity index using HF and HCN as electrophilic partner has been found. Our studies show that the correlation exists only when the interaction is soft–soft in character and for strong bases with weak acids. However, the relationship is not only valid for exothermic reactions as it has been previously postulated but also for endothermic reactions.
Arun
25750 Points
5 years ago
Dear student.....It is not always inversely proportionalwhen compounds in the question have the same nucleophilic centre then nucleophilicity parallels basicity. (EX; CH3O-> CH3COO-)when compounds in the question have different nucleophilic centre but are present in the same group then what you said is true. (how because in this case we target electronegativity)(I->Br->Cl-..larger atomic mass more nucleophilicity)when compounds in the question have different nucleophilic centre and are not in the same group the yet again what you said becomes true. (because of electronegativity)
Srvjeet Partap singh
11 Points
5 years ago
Dear student to know about basicity you must first know about acidity when the positive charge on an electronegative element increases it leaves a proton H+
Which makes it acidic and this increased positive charge is called electrophillicity
The converse is in case of bases when electrophillicity increases the compound leaves H+ and hence the basicity decreases as acids leave a proton and hence the basicity is inversely proportional to electrophillicity 
And I m just 16 doesn't mean I can't be knowledgeable 
Tnx
Rohit
103 Points
5 years ago
In most of the cases nucleophilicity is directly proportional to basicity. But there are some trends in which the may be inversely proportional.
For example as we go down the group basicity tends to decrease but nucleophilicity increases.
There are many such trends. For more details in trends in nucleophilicity refer: NCERT Chemistry Std.12 th part 2. Chapter is Alcohols Phenols and Ethers. Most of ur doubts might get resolved if u overwiew these trends.
Hope it helps.
Regards 
Rohit.

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