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54c) Fill in the blanks. 1 Cl2 FeCl3 2 Cl Cl CH3CH2CH2COCl AlCl3 O Zn(Hg) HCl Cl 3 f) 2 1 CH3Cl AlCl3 SO3 H2SO4 SO3H 3 KMnO4 CO2H SO3H 1 j) CH3 2 CH3 SO3 H2SO4 CH3Cl AlCl3 SO3H Cl2(excess) FeCl3 Cl Cl SO3H CH3 4 CO2H KMnO4 Cl 3 Cl SO3H 1 k) 2 HNO3 H2SO4 (CH3)2CHCl AlCl3 NO2 Cl2 FeCl3 5 Br KOCH3 Cl NO2 Cl NO2 4 3 Br2 hv Cl NO2 1 55d) 2 CH3Cl HNO3 AlCl3 H2SO4 O2 N KMnO4 4 CO2H CO2H Sn/HCl H2N O2N 3 1 f) 2 O O CH3CH2COCl AlCl3 Br2 Br FeBr3 NH2NH2 -OH Br Br NO2 H2 Pd-C HNO3 H2SO4 4 Br 5 NH2 3 j) 1 O O CH3CH2CH2COCl AlCl3 2 HNO3 H2SO4 O2N NH2NH2 -OH 3 4 H2 Pd-C O2N H2N 1 k) 2 CH3CH2CH2COCl O AlCl3 O Cl2 FeCl3 Br2 Cl HO hv O 3 4 -OH Cl Br O POC Cl O 5 Cl O Oxidation and Reduction Oxidation of Alcohols • Alcohols are oxidized to a variety of carbonyl compounds. Oxidation and Reduction Oxidation of Alcohols • Recall that the oxidation of alcohols to carbonyl compounds is typically carried out with Cr6+ oxidants, which are reduced to Cr3+ products. • CrO3, Na2Cr2O7, and K2Cr2O7 are strong, nonselective oxidants used in aqueous acid (H2SO4 + H2O). • PCC is soluble in CH2Cl2 (dichloromethane) and can be used without strong acid present, making it a more selective, milder oxidant. Oxidation and Reduction Oxidation of 2° Alcohols • Any of the Cr6+ oxidants effectively oxidize 2° alcohols to ketones. Oxidation and Reduction Oxidation of 1° Alcohols • 1° Alcohols are oxidized to either aldehydes carboxylic acids, depending on the reagent. or Oxidation and Reduction Oxidation of 1° Alcohols 58a) 2 1 Br Br2 hv CH3CH2Cl AlCl3 KOR Br Br 4 3 2 NaNH2 5 Br2 Alkyl Halides and Elimination Reactions E2 Reactions and Alkyne Synthesis • A single elimination reaction produces a bond of an alkene. Two consecutive elimination reactions produce two bonds of an alkyne. Alkyl Halides and Elimination Reactions E2 Reactions and Alkyne Synthesis • Two elimination reactions are needed to remove two moles of HX from a dihalide substrate. • Two different starting materials can be used—a vicinal dihalide or a geminal dihalide. Alkyl Halides and Elimination Reactions E2 Reactions and Alkyne Synthesis • Stronger bases are needed to synthesize alkynes by dehydrohalogenation than are needed to synthesize alkenes. • The typical base used is ¯NH2 (amide), used as the sodium salt of NaNH2. KOC(CH3)3 can also be used with DMSO as solvent. Alkyl Halides and Elimination Reactions E2 Reactions and Alkyne Synthesis • The reason that stronger bases are needed for this dehydrohalogenation is that the transition state for the second elimination reaction includes partial cleavage of the C—H bond. In this case however, the carbon atom is sp2 hybridized and sp2 hybridized C—H bonds are stronger than sp3 hybridized C—H bonds. As a result, a stronger base is needed to cleave this bond. Alkyl Halides and Elimination Reactions E2 Reactions and Alkyne Synthesis Figure 8.9 Example of dehydrohalogenation of dihalides to afford alkynes b) CH NaH 1 C 2 CH3CH2Br Alkynes Introduction to Alkyne Reactions—Acetylide anions • Because sp hybridized C—H bonds are more acidic than sp2 and sp3 hybridized C—H bonds, terminal alkynes are readily deprotonated with strong base in a BrØnstedLowry acid-base reaction. The resulting ion is called the acetylide ion. Alkynes Reactions of Acetylide Anions • Acetylide anions react with unhindered alkyl halides to yield products of nucleophilic substitution. • Because acetylides are strong nucleophiles, the mechanism of substitution is SN2, and thus the reaction is fastest with CH3X and 10 alkyl halides. Alkynes Reactions of Acetylide Anions • Steric hindrance around the leaving group causes 2° and 3 ° alkyl halides to undergo elimination by an E2 mechanism, as shown with 2-bromo-2-methylpropane. • Thus, nucleophilic substitution with acetylide anions forms new carbon-carbon bonds in high yield only with unhindered CH3X and 1° alkyl halides. Alkynes Reactions of Acetylide Anions • Acetylide anions are strong nucleophiles that open epoxide rings by an SN2 mechanism. • Backside attack occurs at the less substituted end of the epoxide. 1 h) Cl Cl2 HNO3 H2SO4 2 Cl FeCl3 NO2 Br2 hv Cl 4 Cl 3 KOR Br NO2 NO2 mClPBA Cl Cl HO 5 6 H2O O NO2 NO2