Ch 11 - reactions of alcohols

Ch 11 - Reactions of Alcohols
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Unformatted text preview: 1 1 Reactions of AlcohoLs A lcohols are important organic compounds because the hydroxyl gRoup is easily converted to almost any other functional group. In Chapter 10, we studied reac- tions that form aLcohoLs¡ In this chapter, we seek to uNderstand how aLcohoLs react and wH¢ch reagents are best for converting them to other kinds of compounds¡ Table 11£1 summa¤zes the types of reactions aLcohoLs undeRgo and the products that resuLt¥ TABLE ¡ ¡ -¡ Types of Reactions of Alcohols R - OH type of reaction PROduCT 0 dehydration esteRifcatIoN II ¡ - OH alke¢es ¡ - OH ¡ O-C-£' ¡ esteRs oxIdation ¡¤OH KeTo¢es, aLDe¥yDes¦ a§IDs ¡¤OH tosy¨at©o¢ ¡¤Oªs substITutio¢ Tosy¨ate esteRs ¡ - OH ¡ - OH 11-1 Oxidation States of AlcohoLs and ReLated FunctionaL Groups 460 ¡¤X ha¨Ides (good ¨eaving g«oUp) «eduction (I) FoRm al¬ox­de ¡¤H ¡¤OH ¡ ¡-O-¡' a¨kanes ®2) ¯°± e²heRs Ox¦dation of alcohoLs leads to ketones, aLdehydes, and caRboxylic acids¥ These func§ tional groups, in tuRn, undergo a wide variety oF additionaL reactions¥ ¨oR these rea© sons, alcohol oxidations are some of the most common organic reactions. ªn inorganic chemistry, we think of oxidation as a loss of eLectrons and Reduction as a gain of electrons« This pictUre woRKs well For inorganic ions, as when Cr 6 + is redUced to CR 3 + ¬ Most organic compounds are unchaRged, However, and gain oR Loss of eLectRons is not obvious¡ Organic chem­sts tend to think of oxidation as the ResuLt of adding an oxidizing agent (°2, Br2, etc¥), and reductIon as thE resuLt of adding a reducing agent (®2, ¯aB®4, etc.). Most organic chemists habituaLLy use the following simpLe rules, based on the change in the formula of the substance: OX¡DAT¡ON: add±tion of ° oR 02; addition oF X2 (Ha²ogens); loss oF ³ 2¬ REDUCT¡ON: add±t±on of ®2 (oR ® ´ )µ Loss of ° oR 02µ Loss oF X2« NE¡THER: addition oR ²oss oF ® + ¶ ®20, ®X, etc« iS ne±theR an ox±dation nor a Reduct±on¥ 11-1 OxidatIon StaTes of AlcohoLs and ReLaTed FuncTIonaL Groups 461 H I R- C - H i H alkane no bonds to 0 H I R- C - R' I H alkane no bonds to 0 H I R - C ¡ R' i R" alkane No bonds to 0 [0] -¡ ¡0¢ ¢£ ¢ H I R ¡ C- H I H primary aLcohol o¡e bond to 0 ¢ H ¡ R¡ C - R' i H secondary alcohol one boNd to 0 ¡0] ¤¥ ¢ H i R ¡ C - R£ i R¤ tertIary a¢cohol oNe bond to 0 £0¤ ¦§ o II R ¡ C ¡ H + H20 aldehyde Two bonds to 0 o R -- R¥ + H2 0 ketoNe two bonds £o 0 ¡0] -¢ o ¡i R - C ¡ ¢H carboxylIc acId tHree bonds to 0 (no ¦u§t¨e© oxidation) (usually no ªu©t¨e© oxidation« We can telL that an oxidation or a Reduction of an aLcohoL has taken pLace by counting the numbeR of C - 0 bonds to the caRbon atom. FoR example, in a pRimary alcohol, the carbinol ( C - ¢H ) carbon atom has one bond to oxygen; in an aldehyde, the carbonyL carbon has two (moRe oxidized)¡ and in an acid, it has thRee. Oxidation of an alcohol usu- aLly converts C - H bonds to C - 0 bonds¢ If we conveRt an alcohoL to an aLkane, the ...
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