Bromides alcohols

Ethyl bromide Alcohol bromination Special HBr reactor anhydrous HBr plant... 

Initially it was believed252 that hydroxyl radicals were the first formed products in these reactions but lack of any effect on the rate of the reaction by adding bromide, alcohols or benzene demonstrated that this was not the case. Furthermore, hydroxyl radicals react rapidly with [Ru(bipy)3]26 to give a complex with Amax = 750-800 nra which is similar to an intermediate in... 

B-ll. All of the following compounds react with ethylmagnesium bromide. Alcohols are formed from four of the compounds. Which one does not give an alcohol ... 

Sn2 reactions can occur at elements other than carbon. Common examples in organic chemistry are silicon, phosphorus, sulfur, and the halogens. The formation of the tosylate above by attack of the alcohol on TsCl is an example of an Sn2 reaction at sulfur. Later in this chapter you will see that alcohols attack phosphorus very easily and that we use the reaction between ROH and PBra to make alkyl bromides. Alcohols also react rapidly with Si-CI compounds such as MegSiCI to give silyl ethers by an Sn2 reaction at silicon. You have already seen several examples of silyl ether formation (p. 240, for example), though up to this point we have not discussed the mechanism. Here it is B represents a base such as triethyl amine. 

Alkyl bromides. Alcohols are converted into bromides by reaction with bromotrimethylsilane (1.5-4 equiv.) in CHCI3 at 25-50° (equation I). The reaction occurs with inversion. Tertiary and benzylic alcohols react more rapidly than primary or secondary alcohols. Bromides are not formed under the same conditions from Irimethylsilyl ethers of alcohols. However, trimethyl orthoformate is converted into methyl formate, HC(OCH3)3 —s HCOOCH3. Unlike iodotrimethylsUane, the bromosilane does not dealkylate esters, ethers, or carbamates. 

Methyl Hydrc en Methylozonimn bromide alcohol bromide... 

Solubility of Magnesium Bromide Alcohol Compounds in the Corresponding Alcohols. 

It is evident that if a mixture contains two or more constituents which are members of the same class of compounds or are soluble in the same reagents, separation can not be effected in the way outlined. In such cases fractional distillation or crystallization must be resorted to. A thorough knowledge of the properties of compounds is of great value in the examination of mixtures, and is of service in the purification of compounds. The purification of ethyl bromide prepared from potassium bromide, alcohol, and sulphuric acid, is an example. The bromide prepared in this way may contain ether, which is separated with difficulty from the halide by distillation. When the mixture is shaken with concentrated sulphuric acid, the ether dissolves and the bromide is unaffected. In effecting the separation of compounds it is often necessary to convert them into other substances. Thus, acetone can be separated from many other substances which are soluble in water by converting it into the difficultly soluble addition-product with sodium hydrogen sulphite. 

Formation of Alkyl Bromides. Alcohols react with excess TMS-Br (1.5-4 equiv) at 25-50 °C to form the alkyl bromide and hexamethyldisiloxane (eq 12). Benzylic and tertiary alcohols react faster than secondary alcohols. 

Sodium boron hydride lithium bromide Alcohols from carboxylic acid esters s. 11,110... 

In the reaction with methoxybenzaldehyde, bromination of the carbonyl group takes place more rapidly than demethy-lation therefore benzal bromide formation is generally observed in the reaction with aromatic aldehydes. Cleavage of r-butyldimethylsilyl ethers or r-butyldiphenylsilyl ethers occurs at the C-O bond to give alkyl bromides. Alcohols can be converted to alkyl bromides by this method. 

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