Why is naoh added to hmda

Lee, H. Park, J. Han and J. Lee, React. To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given.

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Issue 2, You have access to this article. Please wait while we load your content A high ammonia to dibromohexane ratio is necessary for good yields since low ratios lead to extensive polyamine formation.

As will be shown below, very low yields are obtained when the reaction pressure is below about p. In a preferred embodiment, an inert gas such as nitrogen is employed to increase the pressure in the reaction vessel.

The higher range of temperature permits reaction times as low as five minutes while the lower range requires up to five hours for good results. When sulfuric acid is employed to regenerate HBr in the recovery step, best results are obtained if the acid is of a concentration of from 92 to percent, preferably 96 percent. The following examples, in which all parts are by weight, illustrate specific embodiments of the invention. Example 1 Toluene parts and 1,5-hexadiene 41 parts are charged to a reactor and the solution is cooled to 5 C.

A solution of benzoyl peroxide 2. After this time, reaction is allowed to continue at C. Yield is The 95 pure 1,6-dibromohexane parts and liquid ammonia parts are charged to an autoclave and pressured to p.

The autoclave is heated to C. The autoclave is quickly cooled to ambient temperature, excess ammonia is vented, and residual contents are mixed with parts of 50 wt.

Example 2 Toluene 41 parts and 1,5-hexadiene 41 parts are charged to a reactor and the solution cooled to 20 C. Anhydrous HBr 85 parts is added over a 23 hour period of time in the presence of UV radiation. The crude 1,6-dibromohexane parts and liquid ammonia parts are charged to an autoclave and pressured to p. This autoclave is quickly cooled to ambient temperature and excess ammonia vented. After a slight endothermic reaction, the mixture is gradually heated to about C.

The resulting residue about parts containing HMDA- 2H SO parts is dissolved in water parts and reacted with calcium hydroxide 75 parts slurried in water parts.

The water from the filtrate is removed by azeotropic drying with heptane parts and HMDA The following examples illustrate the improved and unexpected results obtained when the reaction vessel pressure is increased to above p.

Example 3 1,6-dibromohexane The autoclave is quickly cooled to ambient temperature, excess ammonia is vented and residual contents are mixed with Water 20 parts. Example 4 The process of Example 3 is repeated without prepressuring with nitrogen, p. From the 1,6-dibromohexane The following example illustrates an alternate procedure for recovery of HMDA when prepared by the procedure employed in Example 1.

Example 5 A. The mixture was heated and the azeotrope distilled using a plate vacuum jacketed Vigreux column giving an anhydrous slurry. The water layer of the azeotrope contained one part 0. The anhydrous slurry was filtered through a steam heated filter funnel and the filter cake washed with toluene parts at 50 C.

The filtrate consisted of HMDA parts Azeotropic removal of water resulted in an 0. Filtration of the resulting anhydrous slurry gave parts The following example illustrates a typical procedure [for regeneration of HBr from sodium bromide recovered in Examples 1 and 3.

Example 6 6. The resulting mixture is heated to C. The CaSO- is separated by filtration, and the HMDA recovered from its aqueous solution by the azeotropic drying technique outlined above. This procedure, employed in Example 2 is further illustrated in the following example. Example 7 A. The reaction was slightly endothermic. Upon completion of the acid addition, the mixture was gradually heated to about C. Hydrogen bromide HMDA