Propene reaction with bromine

The analogous reaction with bromine was carried out in solution at — 78 °C and gave predominantly the cyclopropane derivative 3. Isomeric byproducts were the cyclobutane 4 and 3-bromo-2-(bromomethyl)propene (5, X = = Br) which were formed in 5-25% yield. ... 

The routes and have both been considered for the reaction between propenal (R = H) and trimethyl phosphite, and hydrolysis of the oxyphosphorane yielded 3-(dimethoxyphosphinoyl)propanal. The phosphorane, 580 (R = Et), obtained from triethyl phosphite and but-3-en-2-one has been mentioned earlier in connection with the synthesis of phosphonic diesters possessing both oxo and hydroxy groups" as an example of its further usefulness through treatment with an electrophile, its reaction with bromine yields the bromo ester 581 and this, when heated, undergoes dehydrobromination to give diethyl (3-oxobutenyl)phosphonate (582), also obtained when 580 is heated with nbs. ... 

Allylic hydrogens are especially reactive in radical substitution reactions. We can synthesize allylic halides by substitution of allylic hydrogens. For example, when propene reacts with bromine or chlorine at high temperatures or under radical conditions where the concentration of the halogen is small, the result is allylic substitution. 

Other alkenes undergo similar reactions with bromine in solution in hexane. For example, propene reacts to give 1,2-dibromopropane, and but-2-ene to form 2,3-dibromobutane ... 

When propene reacts with bromine or chlorine at low temperatures, the reaction that takes place is the usual addition of halogen to the double bond ... 

Bromination of the methyl group of (249) with A -bromosuccinimide, followed by reaction with excess secondary amine gave (250) which shows combined analgesic and antitussive properties. The Reformatsky reaction has also been used for the preparation of 2-amino-ethyl 3,3-diaryl-3-hydroxypropanates (251) as well as their dehydration products. The propene amides (252) have also been prepared for pharmacological evaluation. In l-methyl-3-bis (2-thienyl)-... 

The following illustrates the hydrogenation and halogenation, with bromine, of the alkene propene. Notice that the —CH3 group, which is not a functional group, does not change during either reaction. 

The method lacks general applicability, since mixtures of regioisomers and brominated materials were obtained by reaction with propene and 2-methylpropene, respectively38. 

Ill) Write an equation for the reaction of propene with bromine. Name the product. 

A comparable reaction takes place when propene is treated with bromine at an elevated temperature. 

With hydrogen bromide (HBr), allyltrimethylsilane [CH2=CHCH2Si(CH3)3] yields 2-bromo-l-(trimethylsilyl)propane (Equation 10.91) however, with hydrogen chloride (HCl), the same substrate yields chlorotrimethylsilane and propene (Equation 10.92). This has led some observers to conclude that the reaction with hydrogen bromide (HBr) is not an ionic process beginning, for example, with proton transfer from HBr to the substrate, but rather that the reaction is a radical reaction (of hydrogen and bromine atoms), which simply adds in what appears to be a Markownikoff fashion as a result of stabilization by silicon (see Russell and Nagpal, 1961). 

However, when propene reacts with chlorine or bromine at very high temperatures or under conditions in which the concentration of the halogen is very small, the reaction that occurs is a substitution. These two examples illustrate how we can often change the course of an organic reaction simply by changing the conditions. (They also illustrate the need for specifying the conditions of a reaction carefully when we report experimental results.)... 

Usingstructural formulae throughout, give balanced symbol equations forthe following reactions, a Propene with bromine. 

A novel synthesis of isoselenazoles (150), using bromoseleno-intermediates in the final cyclization stage, comprises the successive treatment, at -80 C, of selenoethers of type (148), e.g. cis-/3-methylseleno-2-propenal, with bromine and ammonia it generally affords the desired heterocycles in very good yield. The precursors (148) are ultimately derived from the appropriate ketones (146), which are first converted into the chloro-aldehydes (147) by the Vilsmeier-Haack reaction, and then treated with methaneselenol in pyridine-triethylamine. They arise as mixtures of cis- and trans-isomers, separable by spinning-band fractional distillation. The u.v. and n.m.r. spectra of the isoselenazoles were recorded and discussed. ... 

If. instead of CC14. water is used as the solvent in a halogen addition reaction, a halohydrin is formed. The student proposed that such a reaction would follow Mechanism A with water replacing bromine as the nucleophile. If this hypothesis is correct, which of the following is the most likely product for the addition of bromine to propene in water ... 

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