CHM 324 Final

purpose of E12: alcohols as nucleophiles
produce an ester through nucleophilic substitution
E12: alcohols as nucleophiles overall reaction
1-butanol + acetic acid = butyl acetate
E12: which layer is on bottom
water b/c butyl acetate is less dense
IR range for alcohol
3200-3650
IR range for carboxylic acid
2400-3400 & 1700-1725
IR range for C-O ester
1000-1300 & 1730-1750
E12: why alcohols can be nucleophilic
– lone pairs on oxygen
– attack electron-deficient atom (usually C in C=O bond)
E12: when alcohols react with carbonyl groups of carboxylic acids…
…a nucleophilic substitution occurs, in which the alcohol replaces the OH of the carboxylic acid, producing an ester
E12: two strategies for overcoming limitations in equilibria in synthesis
– use one reactant in excess
– remove product as it is produced
E12: why does the acid remain in the flask
it isn’t volatile
E12: why does the acid remain in the flask
it isn’t volatile
potassium permanganate test
positive = stays purple, no C=C
negative = changes to brown, precipitate, C=C
Williamson synthesis goes through a _____ reaction
Sn2 between a good nucleophile and a suitably alkyl halide
Williamson ether: which is nucleophile and which is alkyl halide?
phenoxide ion (ArO-) is nucleophile
methyl iodide is alkyl halide
role of PTC in Williamson ether synthesis
– to transfer the phenoxide ion from the aqueous phase into the organic phase where the Sn2 reaction occurs
– after the first NaOH solution is added, two layers are formed, with CH3I on bottom and NaOH on top
o two layers are not miscible, so the ArO- will not come into contact with the CH3I, meaning the reaction won’t happen
o the PTC has dual solubility
• soluble in organic layer because of 4 butyl groups
• soluble in aqueous layer because of ionic character
purpose of Williamson ether synthesis
synthesize an ether, using an Sn2 reaction, and then purify the product using chromatography column with silica gel. The reactant is 4-ethylphenol and tetrabutylammonium bromide and methyl iodide catalyst and react with it, respectively, forming methyl p-ethylphenyl ether. Then characterize by IR.
column chromatography
– based on polarities
– silica gel is polar & keeps polar molecules
– nonpolar molecules pass through
in Williamson ether synthesis, name 4 potential nucleophiles
ArO-, Br-, I-, OH-