Question

4. Rank the bold-faced hydrogens for the following compounds from most acidic to least acidic. нн H H -CH3 'N CH >ICH3 COO-H Ph I II III IV V

Answer 1

H -H politin H . Here, و 2 6. The hydrogen in (1) Structure The higher the s-Character of a bond to more acidic it will be a H MH ... CH3 nod (5) Ph (II) (19) o is alkane hydrogen The hydrogn in (11) Structure is alkene hydrogen and the ne hydrögn the hydrogn in (Iv) in is alkyne in Structure (1) , Hydrogen attached with P De sp3 Carbon in structure (11) hydroon attached with Co a sp~ Carbon ) and in hydrogen attached Structure (1) with a sp3 Carbon. so if any it arom is atom or group of atoms "Acidic hydrogn means, it has a tendency to be released as itt ion. attached to another with hygir electronegativity, the H-atom is porin rial acidic H-atom. a hydrogen, CS Scanned with CamScanner

sp3 < spr 25 Pka Most acidic (159) (IV) < sp. 250). 33).S : 50% s s character Character Characror sie all 50 42 Decreasing acidity The acidity depends to the Stability of the conjugare base. The Stability of conjugate base depends on how well it can accomodate its pair of electrons. The more s character in the orbital, the closer the elections will be to the nuclius, and the in energy, more stabil. The high level of s character in an sp hybridized of the Carson the Overlap region 6 bond to snift much closer to the carbon atom, between t this thirce I ft > t ر Lower causes IV > W NOP CH3 61) Removal or a Proton (H+) decreases the formal charge on an atom by maicule un by one unit. Here, protonated amine bears (+1) Charge The removal of Ht is easiest to do when an charse bears a a tom + Pka vaniu of aquine 9.2 Pronared greater than Iv Acidity of II is CS Scanned with CamScanner

Here,'? more acidic tran To Irond is Slighigy İV, 155, I Protonated amine hydrogen more acidic that alkyne Hydrogen, alkene hydrogen Ydyn and alkane Here, wis more El electronegative than c and N-H bond is weaner than a bond hydrogen an C-H - Ti ID >:155 > 1 Pka 9.2 25 42 50 Now, lili cro-H Fox) toy are Hydrogen atoms attached to oxygen atoms acidic. st is because on removal of the hy drogen atom The negative Charge of left on the viel as proton, CS Scanned with CamScanner

ó;-) 10 oxygen atom is readily stabllised due to the high electronegativity of the oxygen Increase the stability of the conjugate base will increase acidity. [ Moins bo Resonance will increase the stability of the Conjugare base, negative charge can be delocalized. Therefore increasing increasing audity olt Here Pka value is کا Here, in structure (%) the hydrogen is from Carboxy lil qud This hydrogen is Most audic Here Ans It Hand Mil CH3 с. COO-1 50 Pka 5 Pka Most acidic hydrogen Least acidic hydrogen Least acidic order Most acidic to III v> ID ) Iv> Decreaping acidity CS Scanned with CamScanner