Summary of Organic Chemistry II Rxns
No description yet. This curated deck is ready for daily study.
Card preview (24)
What are four methods for preparing alcohols by reduction?
• Reductions of esters by LiAlH4 • Reduction of carboxylic acids by LiAlH4 • Reduction of aldehydes by sodium borohydride (or LiAlH4) • Reduction of ketones by sodium borohydride (or LiAlH4)
What are three oxidation reactions of alcohols?
• Oxidation of primary alcohols to aldehydes by PCC • Oxidation of secondary alcohols to ketones by PCC (or KMno4 or chromic acid) • Oxidation of primary alcohols to carboxylic acids by KMnO4 (or chromic acid)
What are three ways to write chromic acid as a reagent?
• H2CrO4 • K2Cr2O7/H2SO4 • Na2Cr2O7/H2SO4
What are four methods for preparing ethers?
• Williamson Ether synthesis • Ethers from alkene/alcohol • Ethers from alkenes through oxymercuration • Ethers from alcohols through dehydration
Describe the Williamson Ether synthesis
Sn2 reaction between an alcohol and alkyl halide under basic conditions (NaOH). Alkyl group replaces the -H of the hydroxyl group.
Describe how to prepare an ether from an alkene/alcohol
H2SO4 attacked by pi electrons of alkene, forming carbocation. Alcohol acts as nucleophile; loss of proton forms stable ether.
Predict the products for the preparation of an ether from an alkene/alcohol under acidic conditions
Add H and -OR across double bond; -OR adds to the less sterically hindered carbon. Rearrangements possible.
What are the reagents for the preparation of an ether from alkenes through oxymercuration?
• Hg(OAc)2, ROH 2. NaBH4
Predict the products for the preparation of an ether from an alkene/alcohol under acidic conditions
Add H and -OR across double bond; -OR adds to the less sterically hindered carbon. No rearrangements possible.
Describe how to prepare an ether from alcohols through dehydration
Strong acid (H2SO4) and heat protonate alcohol, and a second molecule of alcohol acts as nucleophile to give the ether.
Predict the products for the preparation of an ether from alcohols through dehydration
Alkyl group of R-OH is made into R-O-R; only practical for the synthesis of symmetrical ethers (i.e. one alcohol is used).
What are two methods for preparing epoxides?
• Epoxides from alkenes and peroxyacids 2. Epoxides from halohydrins and base
Predict the product for the preparation of an epoxide from alkenes with peroxyacids
Tether an oxygen between Sp2 carbons
Predict the products for the preparation of an epoxide from halohydrins and base
Tether an oxygen between carbons containing -X and -OH
Why are epoxides highly reactive towards nucleophiles?
The ring strain from 3-membered ring makes it unstable.
Where does the nucleophile attack an epoxide under basic conditions?
Least sterically hindered carbon
Where does the nucleophile attack an epoxide under acidic conditions (and why?)
Epoxide is protonated under acidic conditions and the carbon-oxygen bond will be weaker on the carbon that can best stabilize positive charge; the nucleophile will thus attack the more substituted carbon.
What are two groups to which an alcohol can be converted to facilitate substitution reactions?
• Alcohols to alkyl halides 2. Alcohols to sulfonate (tosylate or mesylate)
What are three reactions used to convert an alcohol to an alkyl halide, and how do they affect stereochemistry?
• SOCl2 or SOBr2 [100% inversion of configuration] • PCl3 or PBr3 [100% inversion of configuration] • HCl/HBr/HI [Sn1 or Sn2 depending on structure of alcohol]
What are two reactions to convert an alcohol to a sulfonate, and how do they affect stereochemistry?
• Mesyl chloride, MsCl [methanesulfonyl chloride] 2. Tosyl chloride, TsCl [p-toluenesulfonyl chloride]
What are five reactions for electrophilic aromatic substitution?
• Chlorination/Bromination • Nitration • Sulfonation • Friedel-Crafts Alkylation • Friedel-Crafts Acylation
What are the reagents for chlorination/bromination EAS reaction?
Cl2/Br2 and FeCl3/FeBr3
What are reagents for nitration EAS reaction?
HNO3 and H2SO4
What are reagents for sulfonation EAS reaction?
SO3/H2SO4