JEE MAIN - Chemistry (2019 - 9th January Morning Slot - No. 7)

The correct decreasing order for acid strength is :
NO2CH2COOH > FCH2COOH > CNCH2COOH > ClCH2COOH
FCH2COOH > NCCH2COOH > NO2CH2COOH > ClCH2COOH
CNCH2COOH > O2NCH2COOH > FCH2COOH > ClCH2COOH
NO2CH2COOH > NCCH2COOH > FCH2COOH > ClCH2COOH

Explanation

After releasing proton (H+) the more stable anion is more acidic nature. The 4 anions are $$ \to $$

JEE Main 2019 (Online) 9th January Morning Slot Chemistry - Basics of Organic Chemistry Question 197 English Explanation

Here $$-$$NO2, $$-$$ CN, $$-$$Cl, $$-$$F all of them have $$-$$ I effective and all have same distance from the anion ($$-$$ O$$-$$).

So depending on which one have more power $$-$$ I effect will be more stable.

Acidic nature $$ \propto $$ $$-$$ I power.

$$-$$ I power order :

$$-$$ NO2 > $$-$$ C $$ \equiv $$ N > $$-$$ F > $$-$$ Cl

So, acidic strength order $$ \to $$

NO2 $$-$$ CH2 $$-$$ COOH > NC $$-$$ CH2 $$-$$ COOH
> F $$-$$ CH2 $$-$$ COOH > Cl $$-$$ CH2 $$-$$ COOH

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