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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Shib Sagar posted an Question
September 18, 2020 • 22:06 pm
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30 points
30 points
- IIT JAM
- Chemistry (CY)
Para chloro benzoic acid vs para fluro benzoic compare the acidity
para chloro benzoic acid vs para fluro benzoic compare the acidity
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Priyanshu kumar Best Answer
Halogens show two types of effects when attached to a phenyl group: 1. —I effect (Inductive effect) which deactivates the rings by pulling electrons towards it and increases the acidity (reduces pH) 1. + M effect (Mesomeric effect) because of presence of lone pair of electrons which activates the ring and decreases acidity (increases pH). Fluorine is more electronegative than chlorine, so logically, fluorobenzoic acid should be a stronger acid than chlorobenzoic acid. This is not the case. Inspite of being more electronegative than chlorine, fluorine has a stronger +M effect because of resonance between 2p orbital of fluorine and 2p orbital of the carbon attached to it. This +M effect is weaker than that of chlorine which is caused due to resonance between 3p orbital of chlorine and 2p orbital of carbon. Hence, p-fluorobenzoic acid is a weaker acid than p-chlorobenzoic acid.
I didn't understand
which part?...reply is not going...🙁
inspite of say
see dear shib...in case of fluorine effective bonding occurs due to 2p orbitals of fluorine and 2p orbital of carbon...this doesn't happen in case of chlorine as 3p orbitals is there so no effective bonding occurs...So due to this strongest +M effect occurs in case of fluorine than chlorine and you know +M effect decreases acidity...so it is obvious that para fluoro benzoic acid is less acidic than para chloro benzoic acid
dear shib ye samajh gye ??