2-Butanone structure

Treating 5.5 g of 2-amino-4,5-dimethylthiazole HCl with 0.66 g of solid sodium hydroxide 15 min at 220°C yields 53% of 4.4. 5.5 -tetramethyT 2,2 -dithiazolylamine, whose structure w as proved by identification with the produa obtained from the reaction between dithiobiuret and 3-bromo-2-butanone (467). This result is comparable to the reaction between 2-aminopyridine and its hydrochloride to yield bis(pyridyl-2)amine (468). Gronowitz applied this reaction to 2-aminothiazole, refluxing it with its hydrochloride 4 hr in benzene and obtained the dimeric 2-aminothiazole (236). He proposed a mechanism (Scheme 143) that involves the addition of a proton to the 5-position of the ring to give 234. The carbocation formed then reacts on the 5-position of a second... 

Write the structures of the enol forms of 2 butanone that react with chlorine to give 1 chloro 2 butanone and 3 chloro 2 butanone... 

Write the structures of the enol forms of 2-butanone that react... 

Compare electrostatic potential maps of enolates derived from 2-butanone, 4,4-dimethyl-2-pentanone, 4,4,4-trifluoro-2-butanone and l-phenyl-2-propanone with those of acetone. Which substituents cause significant changes in the electronic structure of these enolates and what are the nature of these changes Justify your answers by making drawings of any important resonance contributors. 

Ketones undergo a reduction when treated with sodium borohydride, NaBH What is the structure of the compound produced by reaction of 2-butanone with NaBH4 if it has an IR absorption at 3400 cm-1 and M+ = 74 in the mass spectrum ... 

The water is added in order to hydrolyze the a-bromodimethyl ketals that have been produced during the reaction. The ease of hydrolysis of these bromoketals depends on the structure of the ketone. With aeetylcyclohexane (1-cyclohexylethanone) or acetylcyclopentane, stirring with water for 10 minutes is sufficient for complete hydrolysis. In contrast, with phenylacetone (1-phenylethanone) or methyl ethyl ketone (2-butanone), after dilution with water, the addition of 10 equivalents of concentrated sulfuric acid with respect to ketone and stirring for 15 hours at room temperature are necessary for complete hydrolysis. 

Distillation to small volume of a small sample of a 4-year-old mixture of the alcohol with 0.5% of the ketone led to a violent explosion, and the presence of peroxides was subsequently confirmed [1]. Pure alcohols which can form stable radicals (secondary branched structures) may slowly peroxidise to a limited extent under normal storage conditions (isopropanol to 0.0015 M in brown bottle, subdued light during 6 months to 0.0009 M in dark during 5 years) [2], The presence of ketones markedly increases the possibility of peroxidation by sensitising photochemical oxidation of the alcohol. Acetone (produced during autoxidation of isopropanol) is not a good sensitiser, but the presence of even traces of 2-butanone in isopropanol would be expected to accelerate markedly peroxidation of the latter. Treatment of any mixture or old sample of a secondary alcohol with tin(II) chloride and then lime before distillation is recommended [3], The product of photosensitised oxidation is 2-hydroperoxy-2-propanol [4]. 

The reaction of ethyl acetoacetate with simple hydroxy ketones has been compared with the corresponding reactions of the ketoses. The results obtained with l-hydroxy-2-propanone and 3-hydroxy-2-butanone, under the same experimental conditions as with D-fructose, establish a parallel between these reactions. However, as in the case of the aldoses, the yield is greater for these simpler hydroxy ketones than for the ketoses.9 The resultant esters, (XV and XVI), were obtained in the form of sirups, but the free acids, (XVII and XVIII), and their phenacyl esters are crystalline. The acids were shown to be identical with those of known structure described in the literature.9... 

The reaction of simple ketones such as 2-butanone or phenylacetone with ,/<-unsaturated ketones gives cyclohexenones when the reaction is effected by heating in methanol with potassium methoxide. Explain how the cyclohexenones are formed. What structures are possible for the cyclohexenones Can you suggest means for distinguishing between possible isomeric cyclohexenones ... 

Additional insight into the factors affecting product structure was obtained by study of the condensation of 2-butanone with benzaldehyde.2... 

Photoisomerization of the unsaturated lactone (200) to the 1,5-cyclo-lactone (201) provides the first example of a Type A rearrangement in an j8-unsaturated lactone. An X-ray structure analysis has confirmed the photoisomerization of the /3-y-unsaturated ketone (202) to the cyclopentanone (203) by a 1,3-acyl shift. A similar rearrangement of the 3-oxo-A "° " -compound (204) to the cyclo-butanone (205) is in contrast with earlier reports of the oxo-di- r-methane rearrangement of 3-oxo-A " Lcompounds on direct irradiation. Benzophenone-... 

These constants, which are related to the structure of the molecules, allow an evaluation of the forces of interaction between the stationary phase and the solute for different classes of compounds. An index with an elevated value indicates that the stationary phase has a strong affinity for compounds that contain particular organic functions. This leads to a greater selectivity for this type of compound. For example, in order to separate an aromatic hydrocarbon contained in a mixture of ketones, a stationary phase for which benzenes have a very different constant than butanone will be selected. These differences in indices appear in most manufacturers catalogues of chromatographic components (Table 2.1). McReynolds constants have more or less replaced Rohrschneider constants, which are based on the same principle but use different reference compounds. 

In structural and synthetic chemistry, we also find instances of reconsideration 3-(3-methoxyphenoxy)-2-butanone gives by ringclosing dehydration a mixture of 2,3-dimethyl-4-methoxybenzofuran and 2,3-dimethyl-6-methoxybenzofuran,101 not just the 6-derivative.102 2-Ethyl-7-methoxybenzofuran is not formylated in position 3 by the Vilsmeier-Haack reaction, but in position 4.10,103... 

Interactions between sodium atoms and C = CH2 units (Na-C 270-2 287.3 pm) are apparent in the crystal structure of the enolate Li2Na4(0-C(=CH2)tBu)6.2 Pr2NH obtained from the reaction between lithium and sodium diisopropylamides and 3,3-dimethyl-2-butanone.119... 

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