2- Nitropropane, bromination

Bromination using NBS has been used to provide acetylpyrazine derivatives from the corresponding ethylpyrazines. Bromination of 2-ethyl-3-methylpyrazine gives 2-bromoethyl-3-methylpyrazine in quantitative yield this may be oxidized using the sodium salt of 2-nitropropane or with pyridine AT-oxide to yield 2-acetyl-3-methylpyrazine in yields of 66 and 25% respectively (Scheme 14). 

Do not use brominated nitropropanes/dioxanes for applications at pH above 8 or temperature above 60°C because of decomposition, or with secondary or tertiary amines or amides because of formation of health hazards [17]. 

Bromo-2-nitropropane-l,3-diol. Organo-bromine group. General-purpose microbiocide, slimicide, and aerobic/anaerobic bactericide. A benefit... 

By UV spectroscopy in aqueous buffers, the secondary IE of six deuteriums on the acidity of 2-nitropropane, a((CH3)2CHN02)/Aia((CD3)2CHN02) was found to be 1.233 0.033, or 1.04 per D.60 The IE was attributed to a hyperconjugative interaction, whereby CH3 stabilizes the C=N+ double bond of the conjugate base, despite the anionic character. The secondary kinetic IEs of four deuteriums on the acid-catalyzed enolization (measured from the rate of bromination, but one that should parallel the equilibrium IE on acidity) of cyclopentyl-2,2,5,5-d4 and cyclohexyl-2,2,6,6-d4 phenyl ketones are 1.21 and 1.41, respectively.61... 

Nitropropane (178 g., 2.0 moles) is added with cooling to a solution of 132 g. (2.0 moles) of 85% potassium hydroxide in 500 ml. of water. The solution is cooled in an ice bath and stirred while 320 g. (2.0 moles) of bromine is added. (Hood.) The rate of addition of the bromine is such that the temperature of the reaction mixture is held in the range 35-40°. Sufiicient solid sodium sulfite is added to the red solution to obtain a colorless mixture, and the heavy oily layer is separated and washed with water. After drying over sodium sulfate, the product is distilled to give an 89% yield of 2-bromo-2-nitro-propane, boiling at 151.7-151.8°/745 mm. 

The anions of nitroalkanes (nitronates) can be used as precursors in a connective and regiospecific synthesis of tetrasubstituted alkenes. They are easily formed on reaction with LiOMe and undergo oxidative dimerization in the presence of bromine. The resultant 1,2-dinitroalkanes (Scheme 37) participate in a reductive elimination involving an rc1 radical chain mechanism when irradiated in the presence of Na2S, PhSNa or the lithium nitronate derived from 2-nitropropane. 

Preparation of Macromolecular Dioxolenium Salts. Living polystyrene prepared by the polymerization of styrene in THF with a-methylstyrene tetramer dianion reacted with a 2.1-molar amount of ethylene oxide for three hours at room temperature a 6.6-molar amount of adipoyl chloride was added, and the mixture was stirred for 20 horns a 20-molar amount of ethylenebromohydrin was added. This mixture was stirred for 44 hours. The bromoethylated polystyrene was precipitated in excess methanol and freeze-dried from benzene in a vacuum system. A 1-nitropropane solution of polystyrene dioxolenium salt was prepared by reaction of bromoethylated polystyrene with silver perchlorate in 1-nitropropane. Silver bromide was removed from the reaction mixture by filtration. Molecular weight of the product was measured by a vapor-pressure osmometer it was 1910 for living polystyrene and 5190 for the bromoethylated polystyrene. Bromine analysis of the bromoethylated polystyrene showed 67.9% of the calculated value. 

B. Brominated nitropropanes/dioxanes are also commonly used to preserve APCs. They have a wide spectrum of activity and are very stable below 60°C and at acidic and neutral pH. Some of these should not be used in products at or above pH8 because of rapid decomposition into formaldehyde and nitrites if formulated in the presence of secondary or tertiary amines or amides, they could induce nitrosamine formation and could represent a health hazard to the consumer [17]. They are also incompatible with certain dyes. 

---