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IMG_0001_NEW_0001 - '6' ril H-C-C-O-H l" H TT...

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Periodic Trends in Strength of Binary Acids: HnX Trvo factors influence binary acid strength: l) Electronegativity Difference (AEN): Bond polarity 2) Bond Dissociation Energy (BDE): Bond'Strength Strong acid readily dissociates = H-X bond breaks easily Large electronegativiry difference I and lorv bond dissociation energy J: strons acid Bond properties shorv periodic tlends Acid strerrgth shorvs periodic trends FI t=t lEl l?l v 5 Trends in Binary Acid Strength Unfortunately it's not quite that simple. .. Look to see which bond properf.v" change dominates . ElectronegativityDifference(AEN) Dominant cause for an increase in acidity as you move left to right in periodic table CHo NH, H"O HF AEN 2.5 3.0 3.5 4.0 BDE (kJ mol-') 438 432 499 569 Acidiry Increases -) Bond dissociation energy (BDE) Dominant cause for an increase in acidity as you move down a column in the periodic table. 2) AEN BDE (kJ mol-') Aciditv 4.0 569 a a! J HF J-Z 431 HCI 3.0 367 HBr 2.7 298 HI Strengths of Organic Acids Nlolecular Structure + Acid Strength H
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Unformatted text preview: '6' ril H-C-C-O-H l" H TT H-C-C-O-H Ll Acetic acid: ff" = 1.8 x l0-s Ethanol: K" = 1.3 x l0-16 Whv is acetic acid a much stronger acid? 1) Electronegative O from C:O withdraws electron from O-H bond + weakens boud 2) Strength ofconjugate bases \ *' T;ir:' TT n_i_( .----_ H_i_c' H-c-c-o: I -).,i, I -\, I I Acetate ion Ethoxide ion $glqqed negdLtg_ql4rgg 9n 93ch _olyq.n-= l+rebi!ry togctgp_t o=*-, $eaker conjugate base = stronger acid Lewis Acids and Bases Acids and bases are not limited to HrO* and OH-. Lewis acid-base theory -+ reactions in gases, liquids and solids " l,elvis Acicl : Itllcctron llair Acccptor Posses an incomplete valence shell . Lervis Bnse : filectron P*ir Donor Posses a lone pair of electrons l,eryis ;{cid (A) - Lcwis llase (B:) Reaction B: / \.4 -+ B-A Base donates pair of electrons to form bond : Coordination -> Coordinate Covalent Bond Product: adduct (or addition compound) 8...
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