University:
Kentucky State University
Course:
CHE 302 | Organic Chemistry II
Academic year:

2020
Views:

381

Pages:

16
Author:

Athena Harrison

Pharmaceutical organic chemistry “Thiols and Sulfides” Lecture 8 Thiols and Sulfides • Thiols (RSH), are sulfur analogs of alcohols • Named with the suffix -thiol • SH group is called “mercapto group” (“capturer of mercury”) Sulfides • Sulfides (RSR), are sulfur analogs of ethers • Named by rules used for ethers, with sulfide in place of ether for simple compounds and alkylthio in place of alkoxy Thiols: Formation and Reaction • From alkyl halides by displacement with a sulfur nucleophile such as –SH • The alkylthiol product can undergo further reaction with the alkyl halide to give a symmetrical sulfide, giving a poorer yield of the thiol Oxidation of Thiols to Disulfides • Reaction of an alkyl thiol (RSH) with bromine or iodine gives a disulfide (RSSR) • The thiol is oxidized in the process and the halogen is reduced Sulfides • Thiolates (RS) are formed by the reaction of a thiol with a base • Thiolates react with primary or secondary alkyl halide to give sulfides (RSR’) • Thiolates are excellent nucleophiles and react with many electrophiles Sulfides as Nucleophiles • Sulfur compounds are more nucleophilic than their oxygen-compound analogs • 3p electrons valence electrons (on S) are less tightly held than 2p electrons (on O) • Sulfides react with primary alkyl halides (SN2) to give trialkylsulfonium salts (R3S+) Oxidation of Sulfides • Sulfides are easily oxidized with H2O2 to the sulfoxide (R2SO) • Oxidation of a sulfoxide with a peroxyacid yields a sulfone (R2SO2) • Dimethyl sulfoxide (DMSO) is often used as a polar aprotic solvent Thiols in biological system • In biological system, thiols can be oxidized to disulfide • disulfide formation is • Involved in defining the structure and three-dimensional conformations of proteins • Disulfide formation is also involved in the process by which cells protect themselves from oxidative degradation. Aldehydes and Ketones 10 Carbonyl compounds • The compounds occur widely in nature as intermediates in metabolism and biosynthesis • They are also common as chemicals, as solvents, monomers, adhesives, agrichemicals and pharmaceuticals • planar about the double bond and have bond angles of approximately 120°. • Strongly polarized because of the high electronegativity of oxygen relative to carbon. Examples of carbonyl compounds Amoxicillin Carbonyl compounds reactions 1- Nucleophilic addition reactions 2- Nucleophilic acyl substitution reactions Carbonyl compounds reactions 3- Alpha-Substitution Reactions 4- Carbonyl Condensation Reactions Carbonyl compounds reactions 3- Alpha-Substitution Reactions 4- Carbonyl Condensation Reactions