Organic Chemistry Questions
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when attack takes place at chirality center, inversion of configuration takes place SN2
R-O-R' -> (excess HBr or HI) gives R-X or R'-X, uses proton transfer then SN2
the oxygen can be treated as a substituent (epoxy) on the parent alkane, use numbers to specify position
convert more hindered alcohol into alkoxide, less hindered to its tosylate/alkyl halide, make sure tosylate/halide is a good SN2 substrate
produces a strong alkylating reagent that can add an alkyl group to a variety of nucleophiles
RONa (alkoxide), NaCN (cyanide), NaSH (sulfanide), RMgBr (grignard carbocation), LAH (hydride), could be H3O+, need water in a following step
significant ring strain, so they have a great synthetic utility as intermediates
thiols are more acidic than alcohols, conjugate base is more stable due to larger S compared to O (lower charge density)
primary if primary vs secondary due to steric effect, tertiary if primary vs tertiary due to electronic effect
even though they are generally not good leaving groups, the epoxide reaction is both kinetically (low Ea) and thermodynamically (products lower in energy) favored
name the two alkyl groups attached to the oxygen and add the word ether, name groups in alphabetical order, if symmetrical use dialkyl or just alkyl
ethers are relatively unreactive, so they are often ideal solvents, but they can be cleaved by heating concentrated HBr or HI
at least one of the reagents (or catalyst) must be chiral, the Sharpless catalyst forms such a chiral complex with an allylic alcohol
Br2 gives syn 3 membered ring with Br, water attacks more substituted carbon, deprotonation gives hydroxide, additional deprotonation gives an O electrophile, leaving group leaves and O binds to carbon that leaving group left
hydroxide in an SN2 process opens the ring, resulting alkoxide ion protonated by water
competing elimination with secondary alkyl halide or tosylate gives poor yields
use mercury(II) acetate with alcohol solvent, alcohol will react with intermediate mercurinium ion by attacking the more substituted carbon
relatively unreactive especially towards bases, except for epoxides and so are good solvents
NaH over RX gives ether, deprotonating hydroxide, O anion attacks alkyl halide in SN2 reaction
the acid-catalyzed dehydration of ethanol (proton transfer, SN2 attack, proton transfer), only good for primary alcohols and symmetrical ethers