Question

o orale a. Underline the most acidic hydrogens in each of the molecules. b. Rank the molecules above in order of increasing acidity (least acidic to most acidic). a. b. III, II, II, III, I d. II, 1, 5. Nitroethane [CH3CH, NO, PK, 8.6) is a much stronger acid than ethane (CH,CH.PK, 60). Explain. Consider the reaction below to answer the following question(s). pk = 26 pk = 40 0 L : Lit L H . YHLUN - AH HEN + a. The strongest base in the reaction is: b. The weakest acid in the reaction is:

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Answer 1

olan - ob .. Carboxylic acid dissociates into carboxylate and Htion Stability of anion (conjugate base ) a acidity Bezylic hydrogen are more acidic. Once anion and H+ formed, the anion is stabilised by elctron withdrawing group (CHO) and also stabilised by resonance with phenyl ring, он о O OH + H + H2CYCH + HAC H3CX CH3 H H2CYCH н нө Сн, For CHą hydrogen stabilysed by only one resonance structure. But, CH, hydrogens stabilysed by two resonance structure. Also CH2 hydrogens in between the two elctron withdrawing groups. Because of this reason CH2 hydrogen are more acidic. Option b is correct HH 0 0 VH HACX CH HHCHE acidity increasing order Benzoic acid is more acidic due to easily dissociates and gives H+ Acetylacetalone is more acidic compare to 2-phenylacetaldehyde because of two resonance structures and CH2 hydrogens in between the two elctron withdrawing groups Nitroethane (PKa = 8.6) is more acidic than ethane (PKa = 8.6) HCH ON CH3 - effect Nitroethane is more acidic than ethane due to electron withdrawing effect of NO2 (-1 effect) decrease the electron density of adjecent carbon. So, the hydrogens with attached to carbon become acidic. 6 olie H Lio + HN PKa = 8.6 PKa = 40 LDA = Lithium diisopropylamine B is the strongest base (LDA = Lithium diisopropylamide), atom with negative charge and accepts a H+ is base. LDA is strong base, because of Li is small in size and Nitrogen has two bulky isopropyl groups which make non-nucleophilic more basic due to negative charge D is weak acid (Diisopropylamine), Conjugate acid of strong base (LDA) is weak acid.