Acetone isoprene from

The production of isoprene from acetylene and acetone is also possible. The acetylene is reacted with acetone to produce 2-methyl-3-butyn-2-ol which, by hydrogenation produces 2-methyl-3-butene-2-ol. Dehydration then yields isoprene. 

Takagi, iC, "Single-step synthesis of isoprene , Parekm and Pevochan. Imemat., 12 (11) 62-66 (1972). Heath, A High-puiity isoprene from acetone.acetylene", Chm Engng, 80 (22) 48-49 (1973). 

Preparation of dienes is accomplished by dehydration of diols or ole-finic alcohols. Pinacol, (CHjljCOHCOHfCHjlj, is converted to 2,3-di-methyl-1,3-butadiene by heating with 48% hydrobromic acid or by passing the vapors over activated alumina at 420-470°, Yields of the diene are 60% and 86%, respectively. Aniline hydrobroniide is used as a catalyst in the dehydration of 3-methyl-2,4-pentanediol to 3 methyl-l,3-penta-diene (42%). An excellent laboratory preparation of isoprene from acetone in 65% over-all yield has been described. The last step involves catalytic dehydration of dimethylvinylcatbinol over aluminum oxide at 300° to give isoprene in 88% yield. ... 

Chemical Uses. In Europe, products such as ethylene, acetaldehyde, acetic acid, acetone, butadiene, and isoprene have been manufactured from acetylene at one time. Wartime shortages or raw material restrictions were the basis for the choice of process. Coking coal was readily available in Europe and acetylene was easily accessible via calcium carbide. 

Synthesis of P-Methylheptenone from Petrochemical Sources. p-MethyUieptenone (1) is an important intermediate in the total synthesis of terpenes. Continuous hydrochlorination of isoprene [78-79-5] produces prenyl chloride [505-60-6] which then reacts with acetone with a quaternary ammonium catalyst and sodium hydroxide to give P-methyUieptenone (6-methyIhept-5-en-2-one [110-93-0]) (eq. 1) (16—19). 

Apart from these findings, the limited application of ZnCl2 (cyclopropanation of some cyclic 1,3-dienes, isoprene and ethyl vinyl ether 4S-49)) and copper(II) acetyl-acetonate (cyclopropanation of enamines 50)) still stand alone. 

It was a good idea, but it didn t work. No microbe that Weizmann tried yielded isoprene. But Clostridium aceto-butylium did convert starch into a mixture of ethanol, acetone, and butanol, a blend that did not particularly interest Weizmann. It certainly interested Lloyd George, however he heard the whole account from Weizmann himself. Here, pehaps, was a way to produce the acetone that they sorely needed for the manufacture of cordite. Weizmann was asked to scale up his experimental process, and within a short time he d converted a gin distillery into a factory to make his mixture. He easily separated the acetone through distillation, and soon mass production was under way. There was no need for butanol, and huge stocks built up. But after the war the... 

In the first route, methylbutenol is made from acetone and acetylene followed by hydrogenation. Reaction with methyl isopro-penyl ether yields methylheptenone (6). The second route involves the reaction of isobutylene, formaldehyde and acetone (7 ). Methyl vinyl ketone is an intermediate. Finally, methylheptenone is made by alkylation of acetone with prenyl chloride which is derived from isoprene (8). The initial product is the terminal olefin which is isomerized to the desired isopropylidene compound. 

The primary source of isoprene today is as a by-product in the production of ethylene via naphtha cracking. A solvent extraction process is employed. Much less isoprene is produced in the crackers than butadiene, so the availability of isoprene is much more limited. Isoprene also may be produced by the catalytic dehydrogenation of amylenes, which are available in C-5 refinery streams. It also can be produced from propylene by a dimerization process, followed by isomerization and steam cracking. A third route involves the use of acetone and acetylene, produced from coal via calcium carbide. The resulting 3-methyl-butyne-3-ol is hydrogenated to methyl butanol and subsequently dehydrogenated to give isoprene. The plants that were built on these last two processes have been shut down, evidently because of the relatively low cost of the extraction route. 

SIFT-MS was used for the analysis of VOCs present in air samples [127]. Substances such as ammonia, isoprene, acetone, ethanol, and acetonitrile were detected at ppb levels. SIFT-MS was also applied to analysis of blood [126], urine [128], food [129], and headspace from lung cancer cells [130]. The spectrum of exhaled air is presented in Fig. 14.10. 

While caoutchouc was first obtained by polymerizing isoprene it has been found that other hydrocarbons containing the buta i-ydi-ene group will likewise yield caoutchouc. Such hydrocarbons have been obtained from several sources, e.g., turpentiney petroleuniy coaly acetylene. Also compounds related to succinic acid, e.g., pyrotartaric acid (methyl succinic acid) are possible of transformation into isoprene. Levulinic acid, which is aceto propionic acid, CHa—CO—CH2—CH2—COOH, yields a cyclic sulphur compound, methyl-thiophen (p. 853), which, like methyl pyrrolidine, yields isoprene. Ethyl alcohol by conversion into acetone and then by aldol condensation with ethane yields 2-methyl buta 2-ene, CHa—C = CH—CHa which may be transformed... 

The starting material, 2-methyl-3-butyn-2-ol, is made commercially from acetone and acetylene and is convertible into isoprene. This experiment illustrates the oxidative coupling of a terminal acetylene to produce a diacetylene, the Glaser reaction. 

The phosgenation of the tributyltin enolate of acetone led to the same results although some trials performed at low temperature (below - 20°C) showed the possibility to obtain small amounts of isopropenyl chloroformate. It is noteworthy that, in a recent work devoted to a new synthesis of retinal (Vitamin A aldehyde), Bienayme from Rhone-Poulenc (Ref. 117), obtained isopropen-1-yI chloroformate in low yield through phosgenation of the reaction product of tributyltin methoxide with 1-acetoxy isoprene as depicted in scheme 92. 

During World War I German chemists, whose coxmoy was cut off from its sources of natural rubber by the British blockade, polymerized 3-methyl-isoprene (2,3-dimethyl-1,3-butadiene) units, (CH2=C(CH3)C(CH3)=CH2), obtained from acetone, to form an inferior substitute called methyl rubber. By the end of the war Germany was producing 15 tons (13.6 metric tons) of this rubber per month. The USSR (Union of Soviet Socialist Republics), which built a pilot plant at Leningrad (now St. Petersburg) in 1930 and three factories in 1932 and 1933, was the first country to institute a full-scale synthetic rubber industry. 

A compound named y-terpinene, an isomer of a-terpinene, is isolated along with the a isomer from the oils of a number of plant products. Upon ozonolysis, followed by an oxidative workup, yterpinene yields two compounds, one of which is 4-methyl-3-oxopentanoic acid. The second compound is an acid which decarboxylates upon heating and gives acetone. Two structures consistent with the data are possible for yterpinene. What are they On the basis of the isoprene rule, one of them can be discarded as highly improbable. What is the structure of y-terpinene ... 

Biosynthesis See umbelliferone the furan ring originates from activated isoprene (dimethylallyl pyrophosphate). Key step in psoralene biosynthesis is the oxidative dealkylation of (+)marmesine, which in one step is converted to psoralene and acetone by a cytochrome P450 enzyme. 

Sinha, V, J. Williams, M. Meyerhofer, U. RiebeseU, A. I. Paulino and A. Larsen (2007) Air-sea fluxes of methanol, acetone, acetaldehyde, isoprene and DMS from a Norwegian fjord following a phytoplankton bloom in a mesocosm exp>eriment. Atmospheric Chemistry and Physics 7, 739-755... 

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