2-Methyl-l-butenal

Dehydrogenation of Tertiary Amylenes, The staiting material here is a fiaction which is cut from catal57tic clacking of petroleum. Two of the tertiary amylene isomers, 2-methyl-l-butene and 2-methyl-2-butene, are recovered in high purity by formation of methyl tertiary butyl ether and cracking of this to produce primarily 2-methyl-2-butene. The amylenes are mixed with steam and dehydrogenated over a catalyst. The cmde isoprene can be purified by conventional or extractive distillation. 

Methyl Isopropyl Ketone. Methyl isopropyl ketone [563-80-4] (3-methyl-2-butanone) is a colorless Hquid with a characteristic odor of lower ketones. It can be produced by hydrating isoprene over an acidic catalyst at 200—300°C (150,151) or by acid-catalyzed condensation of methyl ethyl ketone and formaldehyde to 2-methyl-l-buten-3-one, foUowed by hydrogenation to the product (152). Other patented preparations are known (155,156). Methyl isopropyl ketone is used as an intermediate in the production of pharmaceuticals and fragrances (see Perfumes), and as a solvent (157). It is domestically available from Eastman (Longview, Texas) (47). 

Further substitution can introduce additional factors, especially nonbonded repulsions, which influence conformational equilibria. For example, methyl substitution at C—2, as in 2-methyl-l-butene, introduces a methyl-methyl gauche interaction in the conformation analogous to B, with the result that in 2-methyl-l-butene the two eclipsed conformations are of approximately equal energy. Increasing the si2e of the group at... 

Methylal, see Dimethoxymethane Methyl alcohol Methyl amyl alcohol Methyl-n-amyl ketone Methyl bromide 2-Methyl-l -butene... 

Chemical Designations - Synonyms Isopropenyl methyl ketone 2-Methyl-l-butene-3-one Chemical Formula CH3COC(CH3)=CHi. 

Methyl-l-butene 2-Methyl-2-butene 3-Methyl-l-butene... 

Dibromo-3-methyl-l-butene 3,4-dibromo-2-methyl-l-butene and l,4-dibromo-2-methyl-2-butene... 

Acid-catalyzed dehydrations usually follow Zaitsev s rule (Section 11.7) and yield the more stable alkene as the major product. Thus, 2-methyl-2-butanol gives primarily 2-methyl-2-butene (trisubstituted double bond) rather than 2-methyl-l-butene (disubstitulecl double bond). 

The complex OsHCl(CO)(P Pr3)2 reacts with 2-methyl-l-buten-3-yne to give the dienyl derivative Os ( )-CH=CHC(Me)=CH2 Cl(CO)(P,Pr3)235 in 86%, which is a result of the selective addition of the Os—H bond of the starting complex to the carbon-carbon triple bond of the enyne (Eq. 4). 

The elongated dihydrogen complex OsCh -fFXCOXP1 Pr3)2 also reacts with 2-methyl-l-buten-3-yne. In toluene at room temperature, the reaction affords the alkenylcarbene derivative OsCl2 CHCH=CMe2 (CO)(P,Pr3)2 in 50% yield, after 1 h (Eq. 7). 

Identity of peaks (1) propane (2) iso -butane (3) n-butane (4) butene-1, butene-2 (5) iso-pentane (6) n-pentane (7) 2-methyl-l -butene (8) 2 -methyl pentane (9) 3-methyl pentane (10) n-hexane (11) methyl cyclopentane (12) benzene... 

Pillai and Pines (84) found that neopentyl alcohol, mixed with 10% by weight of piperidine and passed over alumina prepared from aluminum isopropoxide, yielded 2-methyl-l-butene and 2-methyl-2-butene, in a maximum ratio of 3, and small amounts of 1,1-dimethylcyclo-propane. However, lert-pentyl alcohol yielded these two olefins in a maximum ratio of only 1.4, and none of the cyclopropane was produced (Table VI). Because of these facts a carbonium ion mechanism which is applicable to ferf-pentyl alcohol is not adequate to explain the rearrangement taking place during the dehydration of neopentyl alcohol,... 

In order to explain the structures of the decenes by the action of 75% sulfuric acid on 3-methyl-2-butanol (methylisopropylcarbinol), it is necessary to assume the intermediate formation of 2-methyl-2-butene and 2-methyl-l-butene in the ratio of 3 to 1 ... 

Die Reaktion gelingt nicht mil Alkenen, die an der Doppelbindung verzweigt sind, z.B. 2-Methyl-l-buten, a- und /J-Pinen1. 

The product, BrCH2CBr(CH,)CH,CH3, is a Wc-dibromide formed from the alkene 2-methyl-l-butene,... 

SCHEME 70. Iterative one-pot homologation of terpenoids containing 1,5-diene units with ( )-and (Z)-l,4-diiodo-2-methyl-l-butenes and its application to the synthesis of coenzyme Qs, famesol, and geranylgeraniols171... 

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