3- Hydroxy-4,4-dimethyl-2-pentanone

Reduction of 2-bromo-3-pentanone at mercury affords a mixture of 3-pentanone and l-hydroxy-3-pentanone, whereas electrolysis of Q ,Q -dibromoacetone in the presence of benzoate gives a mixture of products arising from both a carbon-bromine bond cleavage and an Sn2 displacement of bromide by benzoate [94]. In an acetic acid-acetate buffer, branched dibromo ketones, such as 2,4-dibromo-2,4-dimethyl-3-pentanone, are reduced to a-acetoxy ketones however, less highly substituted compounds, such as 4,6-dibromo-5-nonanone, undergo simple cleavage of both carbon-bromine bonds [95]. Other work dealing with the reduction of Q, Q -dibromoketones has been described [96]. 

Figure 3. The effect of water content on the formation of 3,5-dimethyl-l,2,4-trithiolane, 3-Hydroxy-2-pentanone and 2,4-Hexanedione from the reaction of cystine and DMHF.

Enolizable ketones were converted directly into their a-hydroxy dimethyl acetals upon reaction with DIB and methanolic potassium hydroxide at room temperature. If, during work up, there was acid treatment, then a-hydroxyketones were directly obtained. Numerous examples are known for such transformation, e.g. with 3-pentanone, acetophenones, 2,6-diacetylpyridine [16], tropan-3-one [17], -amino-ketones of great structural variety [18], etc. even a free radical reacted successfully in this way [19]. This conversion for an acetyl-oxazole served for the preparation of pyrimidine derivatives. 

Favorskii reported the conversion of 3-hydroxy-4-heptanone to 4-hy-droxy-3-heptanone, as well as analogous transformations of 2-hydroxy-3-pentanone and 2-hydroxy-4,4-dimethyl-3-pentanone. These reactions were carried out at elevated temperatures, in ethanol solutions containing a small proportion of sulfuric acid. At the same time, Favorskii reported the isomerization of 2-hydroxypropiophenone to l-hydroxy-l-phenyl-2-pro-panone under the conditions of yeast fermentation—a claim which the evidence given hardly justified and which von Auwers and Mauss disputed. However, Temnikova reported that this conversion does take place in both acid and alkaline media, and the list of what appear to be... 

The accumulation of thiazoles during the heating of a cysteine Dimethylhydroxy-furanone (DMHF) model system decreased with increasing water content while the accumulation of thiophenones and 3,5-dimethyl-l,2,4-trithiolane had an optimum moisture content (ca. 80%) and 2,4-hexanedione and 3-hydroxy-2-pentanone increased with moisture content [23.24], There is little question that the Aw (or moisture content) influences both the rate of the Maillard reaction and influences the sensory properties of a system on heating. 

The aldol reaction of 2,2-dimethyl-3-pentanone, which is mediated by chiral lithium amide bases, is another route for the formation of nonracemic aldols. Indeed, (lS,2S)-l-hydroxy-2,4,4-trimethyl-l-phenyl-3-pentanone (21) is obtained in 68% ee, if the chiral lithiated amide (/ )-A-isopropyl-n-lithio-2-methoxy-l-phenylethanamine is used in order to chelate the (Z)-lithium cnolate, and which thus promotes the addition to benzaldehyde in an enantioselective manner. No anti-adduct is formed25. 

In the case of boiled beef the results of AEDA were compared with those of AECA. Table 16.4 indicates that they agreed except in three cases. The odour potencies of 4-hydroxy-2,5-dimethyl-3(2H)-furanone, 3-mercapto-2-pentanone and methional were more than one dilution step higher in AECA than in AEDA [56]. Most likely, portions of these odorants had been lost during concentration of the extract for AEDA. AECA was also used in studies on the aroma of pepper [55], coffee [57] and Camembert cheese [58]. 

Cl2N4O2C 3H30, 3-Pentanone, 2-[[3-[[2-(hydroxy imino)-1, l -dimethyl propyl] amino]propyl]amino]-, oxime, dihydrochloride, [104484-57-3], 31 273... 

Rhamnose and proline were reacted under a wide range of reaction conditions with the expectation of producing volatiles of differing type and ratio. Such large differences were desired to give the best opportunity for the empirical models to account for and explain the variation. If valid, the model terms would be expected to account for differences in product composition and perhaps provide insight into the reaction pathways. Some of the 23 volatiles modeled including 2,3-dimethyl-4-hydroxy-3(2H)-furanone (DMHF), 2-acetoxy-3-pentanone, and four 2,3-dihydro-(lH)-pyrrolizines will be discussed below. 

The water content significantly affects the formation of some compounds. Figure 2 shows that the formation of thiazoles decreases as the water content increases. Figure 3 shows the relationship between water content and the formation of a 3,5-dimethyl-1,2,4-trithiolane, 3-hydroxy-pentanone and 2,4-hexanedione. The highest level of trithiolanes was obtained from the sample prepared with 75% water. Figure 4 shows that these three thiophenones were also produced at maximum at 75% water medium. 

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]. 

FIGURE 17.16 Proposed precursor flavor components of 2-acetyl-l-pyrroline, 4-mercapto-4-methyl-2-pentanone, 2-acetyl-l-thiazoline, and 4-hydroxy-2,5-dimethyl-3(2H)-furanone. 

Carbonic acid, dimethyl ester 9.9 Pentanone-2,4-hydroxy-4-methy 1 9.2... 

Scheme 9.47. A schematic representation of the formation of the enolate anion of 2,2-dimethyl-3-pentanone and its reaction at low temperatures with benzenecarboxaldehyde (benzaldehyde) to form eryt/tro-5-hydroxy-2,2,4-trimethyl-5-phenyl-3-pentanone. Under equilibrating conditions (at 25°C), the corresponding threo-ketone, which has the bulky groups farthest apart and thus is most stable, forms.

Dimethyl- 3-pentanone Enolate 5-Hydroxy-2,2,4-trimethyl-3-heptanone (81%)... 

Startg. -keto ester in dimethyl sulfoxide added at 25 under argon during 5 min. to a stirred mixture of benzaldehyde and zinc in dimethyl sulfoxide, and stirring continued 11 hrs. 5-hydroxy-4-methyl-5-phenyl-3-pentanone. Y 92%. F. e. s. T. Mukaiyama et al., Chem. Lett. 1976, 95. 

Formulate a synthesis of 2-hydroxy-2,4-dimethyl-3-pentanone, beginning with simple aldehydes and ketones and using a 1,3-dithiacyclohexane anion. 

The formation of 2,3-dimethyl-N-vinylpyrrole from l-hydroxy-2-methyl-3-butanone oxime and 2-methyl-N-vinylpyrrole from 2-hydroxy-2-methyl-4-pentanone... 

The atmospheric lifetime of 2,4-dimethyl-2-pentanol with respect to reaction with OH radicals is estimated to be 10 h using [OH] = 2.5 x 10 molecule cm and the rate coefficient presented in this section. The product study conducted by Atkinson and Aschmann (1995) using GC-FK) and GC-MS showed that the reaction of OH with 2,4-dimethyl-2-pentanol gives the following products (molar yields) Acetone (92 15%), 2-methylpropanal (21 22%), 4-methyl-2-pentanone (5 1%), and 4-hydroxy-4-methyl-2-pentanone (12 2%). In addition, the yield of a tertiary nitrate was estimated to be 4 1%. 

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