Alcohols phosphorus tribromide

Alcohol Phosphorus tribromide Alkyl bromide Phosphorous acid... 

Benzyl Alcohol Phosphorus Tribromide Phosphorus Tribromide... 

Thionyl chloride and phosphorus tribromide are specialized reagents used to bring about particular functional group transformations For this reason we won t present the mechanisms by which they convert alcohols to alkyl halides but instead will limit our selves to those mechanisms that have broad applicability and enhance our knowledge of fundamental principles In those instances you will find that a mechanistic understand mg IS of great help m organizing the reaction types of organic chemistry... 

Reaction of alcohols with phosphorus tribromide (Section 4 13) As an alternative to converting alco hols to alkyl bromides with hydrogen bromide the inorganic reagent phosphorus tribromide is some times used... 

Reaction with phosphorus trihalides (Section 4 13) Phosphorus trichloride and phosphorus tribromide convert alcohols to alkyl halides... 

Alkyl halides are such useful starting materials for preparing other functional group types that chemists have developed several different methods for converting alcohols to alkyl halides. Two methods, based on the inorganic reagents thionyl chloride and phosphorus tribromide, bear special mention. 

Phosphorus tribromide reacts with alcohols to give alkyl bromides and phosphorous acid. 

Phosphine(s), chirality of, 314 Phosphite, DNA synthesis and, 1115 oxidation of, 1116 Phospholipid, 1066-1067 classification of, 1066 Phosphopantetheine, coenzyme A from. 817 structure of, 1127 Phosphoramidite, DNA synthesis and, 1115 Phosphoranc, 720 Phosphoric acid, pKa of, 51 Phosphoric acid anhydride, 1127 Phosphorus, hybridization of, 20 Phosphorus oxychloride, alcohol dehydration with. 620-622 Phosphorus tribromide, reaction with alcohols. 344. 618 Photochemical reaction, 1181 Photolithography, 505-506 resists for, 505-506 Photon, 419 energy- of. 420 Photosynthesis, 973-974 Phthalic acid, structure of, 753 Phthalimide, Gabriel amine synthesis and, 929... 

Tetrahydroimidazo[5,l-c][l,2,4]triazine 474 was prepared (79KGS1540) by treating imidazole derivatives 472 or 473 with hydrazine. Compound 473 was obtained by reaction of the respective imidazole with 1,2-dibromoethane or by the reaction of the alcohol derivative 471 with phosphorus tribromide. On the other hand, chlorination of471 with thionyl chloride gave 472 (Scheme 100). 

Another general method for converting alcohols to halides involves reactions with halides of certain nonmetallic elements. Thionyl chloride, phosphorus trichloride, and phosphorus tribromide are the most common examples of this group of reagents. These reagents are suitable for alcohols that are neither acid sensitive nor prone to structural rearrangement. The reaction of alcohols with thionyl chloride initially results in the formation of a chlorosulfite ester. There are two mechanisms by which the chlorosulfite can be converted to a chloride. In aprotic nucleophilic solvents, such as dioxane, solvent participation can lead to overall retention of configuration.7... 

In a similar vein, the keto bridge in 5 can be replaced by oxygen with retention of activity. Reduction of acetophenone derivative 19 by means of sodium borohydride leads to the corresponding alcohol (20). Reaction with phosphorus tribromide with cyanide gives... 

Phosphorus tribromide Phosphorus trichloride Propionic acid Propyl acetate Propyl alcohol Propyl bromide Propyl chloride Propyl formate Propyl iodide Sodium... 

In a 2-1. three-necked flask, fitted with a mechanical stirrer (Note 1), a reflux condenser, and a dropping funnel, is placed 630 g. (670 cc., 7 moles) of /3-ethoxyethyl alcohol (Note 2). The stirrer is started, and 600 g. (210 cc., 2.2 moles) (Note 3) of phosphorus tribromide is added from the dropping funnel over a period of one and one-half to two hours. The temperature is permitted to rise until the reaction mixture refluxes gently. 

In a 500-cc. three-necked flask, fitted with a mechanical stirrer, thermometer, separatory funnel, and calcium chloride tube, are placed 96 g. (56.5 cc., 0.36 mole) of redistilled phosphorus tribromide (b.p. 174-175°/740 mm.) and 50 cc. of dry benzene. From the separatory funnel, 15 g. of dry pyridine is added with stirring over a period of fifteen minutes. The flask is then surrounded by an ice-salt mixture, and the contents are cooled to — 5°. A mixture of 102 g. (1 mole) of redistilled tetrahydrofur-furyl alcohol (b.p. 79-80°/20 mm.) and 5 g. of dry pyridine (total pyridine, 20 g., 0.25 mole) is added slowly from the dropping funnel with stirring over a period of four hours. During this time the internal temperature is kept at —5° to —3°. Stirring is continued for one hour longer, and the cooling bath is then allowed to warm up to room temperature. 

Tetrahydrofurfuryl bromide has been obtained in low yields by the action of hydrobromic acid, or of phosphorus tribromide, on the corresponding alcohol.1 The yield is improved markedly by use of phosphorus tribromide and pyridine.2 3 The bromide has also been prepared by the action of potassium hydroxide on 4,5-dibromopentanol-l.4... 

Phosphorus pentafluoride Phosphorus pentasulfide Phosphorus pentoxide Phosphorus, red Phosphorus tribromide Phosphorus bichloride Water or steam Air, alcohols, water Formic acid, HF, inorganic bases, metals, oxidants, water Organic materials Potassium, ruthenium tetroxide, sodium, water Acetic acid, aluminum, chromyl dichloride, dimethylsulfoxide, hydroxylamine, lead dioxide, nitric acid, nitrous acid, organic matter, potassium, sodium water... 

Cinnamyl bromide has been prepared from cinnamyl alcohol by the action of hydrogen bromide in cold acetic acid2 and of phosphorus tribromide in boiling benzene.3 It has also been... 

Reaction with phosphorus trihalides Alcohols are converted to alkyl bromides by reaction with phosphorus tribromide (Refer Unit 10, Class XII). 

The mechanism for the reactions with phosphorus halides can be illustrated using phosphorus tribromide. Initial reaction between the alcohol and phosphorus tribromide leads to a trialkyl phosphite ester by successive displacements of bromide. The reaction stops at this stage if it is run in the presence of an amine which neutralizes the hydrogen bromide that is formed.9 If the hydrogen bromide is not neutralized the phosphite ester is protonated and each alkyl group is successively converted to the halide by nucleophilic substitution by bromide ion. The driving force for cleavage of the C—O bond is the... 

The reaction of phosphorus tribromide with the alcohol above has been reported by Marvel to give the analogous bromide. The use of phosphorus trichloride did not yield the chloride [80]. 

Both reactants in the Williamson ether synthesis usually originate in alcohol precursors. Sodium and potassium alkoxides are prepared by reaction of an alcohol with the appropriate metal, and alkyl halides are most commonly made from alcohols by reaction with a hydrogen halide (Section 4.7), thionyl chloride (Section 4.13), or phosphorus tribromide (Section 4.13). Alternatively, alkyl p-toluenesulfonates may be used in place of alkyl halides alkyl p-toluenesulfonates are also prepared from alcohols as their immediate precursors (Section 8.14). 

---