chapter4

chapter4 - 4-4-1Organic Organic ChemistryChemistryWilliam...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 4-4-1Organic Organic ChemistryChemistryWilliam H. BrownWilliam H. BrownChristopher S. FooteChristopher S. FooteBrent L. IversonBrent L. Iverson4-4-2Acids Acids and and BasesBasesChapter 4Chapter 44-4-3Arrhenius Acids and BasesArrhenius Acids and BasesIn 1884, Svante Arrhenius proposed these definitions acid:acid:a substance that produces H3O+ions aqueous solutionbase:base:a substance that produces OH-ions in aqueous solutionthis definition of an acid is a slight modification of the original Arrhenius definition, which was that an acid produces H+in aqueous solutiontoday we know that H+reacts immediately with a water molecule to give a hydronium ionH+(aq)+H2O(l)H3O+( aq)Hydronium ion4-4-4Brnsted-Lowry DefinitionsBrnsted-Lowry DefinitionsAcid:Acid:a proton donorBase:Base:a proton acceptor+Proton donor Protonacceptor-OHHOHHOHH++OHH+ProtonacceptorProtondonor+OHHOHHNHHHHHH++NHH::::4-4-5Conjugate Acids & BasesConjugate Acids & Basesconjugate baseconjugate base:the species formed from an acid when it donates a proton to a base conjugate acid:conjugate acid:the species formed from a base when it accepts a proton from an acidacid-base reaction:acid-base reaction:a proton-transfer reactionconjugate acid-base pair:conjugate acid-base pair:any pair of molecules or ions that can be interconverted by transfer of a protonHCl(aq)H2O( l)Cl-(aq)H3O+(aq)++WaterHydrogenchlorideHydroniumionChlorideion(base)(acid)(conjugateacid of H2O)(conjugatebase of HCl)conjugate acid-base pairconjugate acid-base pair4-4-6Conjugate Acids & BasesConjugate Acids & BasesBrnsted-Lowry definitions do not require water as a reactantconsider the following reaction between acetic acid and ammoniaNH4+CH3COOHCH3COO-NH3++Acetic acidAmmonia(acid)conjugate acid-base pairAcetate ionAmmoniumion(base)(conjugate baseacetic acid)(conjugate acidof ammonia)conjugate acid-base pair4-4-7Conjugate Acids & BasesConjugate Acids & Baseswe can use curved arrows to show the flow of electrons in an acid-base reaction CH3-C-OOHN HHH CH3-C-O -OH-N-HHH++Acetic acid(proton donor)Acetate ion::::::Ammonia(proton acceptor)Ammoniumion4-4-8Conjugate Acids & BasesConjugate Acids & BasesMany organic molecules have two or more sites that can act as proton acceptorsin this chapter, we limit our discussion to carboxylic acids, esters, and amidesin these molecules, the favored site of protonation is the one in which the charge is more delocalizedquestion: which oxygen of a carboxylic acid is protonated?CH3-C-O-HO+H2SO4CH3-C-O-HHO+CH3-C-O-HHO++ HSO4-orA(protonation on the carbonyl oxygen)B(protonation on thehydroxyl oxygen)4-4-9Conjugate Acids & BasesConjugate Acids & Basesfor protonation on the carbonyl oxygen, we can write three contributing structurestwo place the positive charge on oxygen, one places it on carbonA-1 and A-3 make the greater contribution because all atoms have complete octetsthe positive charge is delocalized over three atoms...
View Full Document

This note was uploaded on 03/21/2008 for the course CHEM 261 taught by Professor Austell during the Spring '08 term at UNC.

Page1 / 29

chapter4 - 4-4-1Organic Organic ChemistryChemistryWilliam...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online