2.2- dimethyl-3- -methylpentane

Alkenes with a 1,1-disubstitution pattern form tertiary carbocations upon treatment with a Brpnsted acid. Consequently, such compounds are often easily reduced (Eq. 72). An example of this is the formation of 2-methylpentane in 93% yield after only 5 minutes when a dichloromethane solution of 2-methyl-1-pentene and 1.4 equivalents of triethylsilane is treated with 1.4 equivalents of trifluoromethanesulfonic acid at —75°.216 Similar treatment of 2,3-dimethyl-l-butene gives a 96% yield of 2,3-dimethylbutane.216... 

The neurotoxicity of pure M-hexane (99%) has been compared to mixed hexanes (a mixture containing the -hexane isomers 2-methylpentane, 3-methylpentane, cyclohexane, methyl cyclopentane, and 2,3-dimethyl butane with approximately 1% -hexane) (IRDC 1981). The mixture was intended to be more representative of products used commercially. In this experiment, groups of Sprague-Dawley rats were exposed to -hexane alone (500 ppm), mixed hexanes (494 ppm) or -hexane plus mixed hexanes (992 ppm) daily for 6 months, 22 hours a day. No deaths occurred as a result of treatment. 

Benzene formation from all isohexanes had a similar energy of activation value. With platinum this was nearly twice as high as that of n-hexane aromatization (62) with palladium black, however, nearly the same values were found for -hexane and isohexanes (97a). This indicates a common rate-determining step for aromatization with skeletal rearrangement. This is not the formation and/or transformation of the C5 ring. We attribute benzene formation to bond shift type isomerization preceding aromatization. It requires one step for methylpentanes and two steps for dimethyl-butanes this is why the latter react with a lower rate, but with the same energy of activation. 

Dimethylpropylmethane, see 2-Methylpentane Dimethyl sulphate, see Dimethyl sulfate... 

The most important flavour compound in raw onions is thiopropanal-S-ox-ide, the lachrymatory factor [145,146]. Other important flavour compounds are 3,4-dimethyl-2,5-dioxo-2,5-dihydrothiophene and alkyl alkane thiosulfonates such as propyl methanethiosulfonate and propyl propanethiosulfonate with a distinct odour of freshly cut onions [35, 36, 147]. Various thiosulfinates that have a sharp and pungent odour may also contribute to the flavour of onions. These compounds, however, are rapidly decomposed to a mixture of alkyl and alkenyl monosulfides, disulfides and trisulfides (Scheme 7.3) of which dipropyl disulfide, methyl ( )-propenyl disulfide, propyl ( )-propenyl disulfide, dipropyl trisulfide and methyl propyl trisulfide are the most important contributors to the aroma of raw and cooked onions (Table 7.5, Fig. 7.6) [148-150]. Recently, 3-mercapto-2-methylpentan-l-ol was identified in raw and cooked onions eliciting intense meat broth, sweaty, onion and leek-like odours [142, 151]. 

Problem 6.13 Give the structural formulas for the alkenes formed on dehydrobromination of the following alkyl bromides and underline the principal product in each reaction (a) 1-bromobutane, (b) 2-bromobutane, (c) 3-bromopentane, (d) 2-bromo-2-methylpentane, (e) 3-bromo-2-methylpentane, (/) 3-bromo-2,3-dimethyl-pentane. ... 

Thermal stability is enhanced in chelates thus dimethyl-2-methylpentane-2,4-dioltitanium [23916-35-0] (22) is muchmore stable than (CH3)3Ti(OCH(CH3)2)2 (68). The structure of the former has been shown by x-ray diffraction to be dimeric and five-coordinate through oxygen bridges. The more highly substituted the six-membered ring, the more thermally stable the compound. 

Problem 4.28 Give topological structural formulas for (a) propane, (b) butane, (c) isobutane, (d) 2,2-dimethyl-propane, (e) 2,3-dimethyl butane, (/) 3-ethylpentane, (g) l-chloro-3-methylbutane, (h) 2,3-dichloro-2-methylpentane, (0 2-chloro-2,4-trimethylpentane. ... 

The major components of the neutral fraction are 2-methyl-propanal, 2-butanone, 3-methylbutanal, 2-methylbutanal, dimethyl disulfide, and 3-methylpentanal. 

PS PS 3-Methylpentane Monochlorobenzene PSF Diethylene Glycol Dimethyl Ether... 

Recently, AEDA and SHA-0 yielded 41 and 45 odor active compounds for Scheurebe and Gewurztraminer wines, respectively (P). Ethyl 2-methylbutyrate, ethyl isobutyrate, 2-phenylethanol, 3-methylbutanol, 3-hydroxy-4,5-dimethyl-2(5H)-furanone, 3-ethylphenol and one unknown compound, named wine lactone, showed high flavor dilution (FD)- factors (Table I) in Gewurztraminer and Scheurebe wines. 4-Mercapto-4-methylpentan-2-one belongs to the most potent odorants only in the variety Scheurebe whereas cis-rose oxide was perceived only in Gewurztraminer (Table I). 4-Mercapto-4-methylpentan-2-one was identified for the first time in Sauvignon blanc wines (JO). The unknown compound with coconut, woody and sweet odor quality, which has not yet been detected in wine or a food, was identified as 3a,4,5,7a-tetrahydro-3,6-dimethylbenzofuran-2(3H)-one (wine lactone) (JJ). 

Other types of sila systems also give di-n-methane products. In the case of (19), irradiation at 10 K in an argon matrix or at 77 K in a 3-methylpentane glass affords the di-n-methane product (20), which on further irradiation or upon heating reverts to the starting material (equation 21). Photolysis of (19) at room temperature gives instead retro Diels-Alder fragmentation to tetramethyldisilene, whose intermediacy was established by means of [4 + 2] cycloaddition with 2,3-dimethyl-1,3-butadiene. ... 

The results of pyrolysis of polypropylene in air depends on the pyrolysis heating rate because the pyrolysis process competes with the oxidation [108], By heating between 120° C and 280° C in air, polypropylene is reported to generate ethene, ethane, propene, propane, isobutene, butane, isobutane, pentadiene, 2-methyl-1-pentene, 2,4-dimethyl-1-pentene, 5-methyl-1-heptene, dimethylbenzene, methanol, ethanol, 2-methyl-2-propene-1-ol, 2-methylfuran, 2,5-dimethylfuran, formaldehyde, acetaldehyde, acrolein, propanal, methacrolein, 2-methylpropanal, butanal, 2-vinylcrotonaldehyde, 3-methylpentanal, 3-methylhexanal, octanal, nonanal, decanal, ethenone, acetone, 3-buten-2-one, 2-butanone, 1-hydroxy-2-propanone, 1-cyclopropylethanone, 3-methyl-2-buten-2-one, 3-penten-2-one, 2-pentanone, 2,3-butanedione [109]. 

DIMETHYL-HEXANE 3-ETHYL-2-METHYLPENTANE 3-ETHYL-3-METHYLPENTANE... 

Photolysis of di-t-butyldiazidosilane at 254 nm in 3-methylpentane glass at 77 K or in an argon matrix at 10 K led to a highly reactive di-i-butylsilylene intermediate with Amax 480 nm. Subsequent irradiation at 500 nm resulted in formation of l-/-butyl-2,2-dimethyl-l-silacyclopropane (95), the first stable silacyclopropane with an Si—H bond (Scheme 27) (88JA6689). 

A solution of l-(3,3-dimethyl-2-phenylcycloprop-l-enyl)-4-methylpentane (188 mg) and thioxanthone (19 mg) in benzene (200mL) was irradiated for 15 min with a 450-W Hanovia lamp with a Pyrex glass filter sleeve. The solvent was removed under reduced pressure and the residue was subjected to column chromatography (silica gel, hexane). The major fraction was the title compound yield 117 mg (63%). 

Me), and the corresponding /rfln5-2,cw-3-dimethyl isomer (7 R = Me, R = H), with tributyltin hydride yielded a mixture of [3- Hi]-3-methylpentanal (8) and [4- Hi]-3-methyl-pentanal (9). From the reaction of the tra/ii-2-cw-3-dimethyl isomer, the ratio of the product isotopomers was 3.5 1, which demonstrated the strong preference of the intermediate radical for cleavage of the cw-methyl-substituted bond. ... 

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