Grignard Synthesis of Various Tertiary Alcohols

Abstract

We have developed a general Grignard procedure for the synthesis of a variety of aliphatic tertiary alcohols, which presents students with an added challenge of product identification. Many organic syntheses in the undergraduate teaching laboratory can be infused with an extra element of discovery simply by not revealing the specific starting materials. Substitutions of isomers or homologues for the prescribed organic reagents create multiple possibilities for unknowns. We have found inclusion of this type of puzzle helpful in combating the tendency of students to approach lab work in a mechanical or cookbook fashion (1, 2).Five articles on Grignard reactions have appeared in this Journal in the last 10 years (2-6). All organic laboratory manuals include at least one Grignard procedure. Phenylmagnesium bromide is the most commonly described Grignard reagent, used in the synthesis of triphenylmethanol (trityl alcohol) and benzoic acid (7-9). Our variation of the standard Grignard reaction incorporates anhydrous techniques, distillation, and infrared analysis to identify an unknown product. ExperimentalProcedure 1 CAUTION: The organic reagents and products in this procedure are flammable. Diethyl ether is highly flammable. Flame drying of glassware should be completed by all students before diethyl ether is dispensed! RX + Mg → [RMgX] + R′R″C=O → [RR′R″COMgX] → RR′R″COH Criteria: RX = C 2 -C 5 1° alkyl bromide (unbranched) R′R″C=O = C 3 -C 5 ketone RR′R″COH = C 6 -C 9 3° alcohol {R, R′, R″ may be the same or different}

Diastereoselective Synthesis of (+/-)-1,2-Diphenyl-1,2-propanediol. A Discovery-Based Grignard Reaction Suitable for a Large Organic Lab Course

“…Diastereomer identification is straightforward, as the mp ranges of (+/-)-2 and (+/-)-3 are separated by 10 °C. 3 The reaction's diastereoselectivity can be rationalized by the preferential addition of MeMgI to the least sterically hindered face of the carbonyl group in a rigid, five-membered cyclic intermediate ((+/-)-4) (the "Cram chelate model") (5, 6 ) (Scheme II). Students encountered few difficulties in either the preparation of MeMgI or its reaction with benzoin.…”

Sintesis Feromon 6-Metil-2-Hepten-4-Ol Dari Krotonaldehid Melalui Pembentukan Reagen Grignard Isobutilmagnesium Bromida

“…Proses sintesis 6-metil-2-hepten-4-ol diawali dengan pembentukan reagen Grignard isobutil magnesium bromide. Kondisi pembentukan reagen Grignard ini harus bebas air, karena reagen Grignard merupakan basa yang sangat kuat dan akan bereaksi dengan air [2]. Reaksi ini bersifat eksotermis karena merupakan reaksi radikal bebas antara logam Mg dengan isobutil bromida.…”

Using a Premade Grignard Reagent To Synthesize Tertiary Alcohols in a Convenient Investigative Organic Laboratory Experiment

“…This Journal has published a number of interesting laboratory experiments utilizing Grignard reagents (1)(2)(3)(4)(5)(6)(7). The importance of utilizing the Grignard reagent is often overshadowed by the preparation of the Grignard reagent itself.…”