Which one is more acidic, p-fluorobenzoic acid or p-bromobenzoic acid and why?
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106The p-orbital overlap is much more effective when the overlapping orbitals are of comparable size and so the +R effect of fluorine (which uses 2p orbital) is greater than the effect of bromine (which uses 4p orbital). Infact, the +R and +I effects of F are nearly counterbalanced, whereas the +R effect of Br is weaker than its +I effect. Therefore, although both halogen atoms tend to lower the electron density of the ring, the lowering is much effective in Br-acid than F-acid. Hence, p-fluorobenzoic acid is LESS acidic than p-bromobenzoic acid.
145p-bromobenzoic acid I guess, as there will be H-bonding in case of p-fluorobenzoic acid
- Bitan Chakraborty There is no relationship of acidity with H-bonding in this case!!!Upvote·0· Reply ·2013-04-16 23:35:28
79p-fluorobenzoic flourine increases electrinegativity.
- Bitan Chakraborty So, how do you explain acidity?
996p bromobenzoic acid will be more acidic as it contains more acidic hydrogen..
In p-fluorobenzoic acid there is backbonding so the acidity decreases
- Bitan Chakraborty Answer is correct but I didn't understand the Back-Bonding concept.
- Swarna Kamal Dhyawala fluorine is very electronegative so it attracts the lone pair towards it so the corresponding carbon becomes electron deficient so fluorine again donates its lone pair that is called back bonding
- Swarna Kamal Dhyawala * attracts the shared paired...
- Bitan Chakraborty Answer the physical question as well!!