Acetone fragmentation

Removal of solvent allows the colloidal particles to grow to a film. However, strongly adsorbed acetone, and perhaps small amounts of acetone fragments or telomers as well, remain in the film affecting its electrical properties. 

Ozonolysis data are used to determine the location of the double bonds. The acetone fragment, which comes from carbon atoms 1 and 2 of 2,6-dimethyloctane, fixes the position of one double bond. Formaldehyde results from ozonolysis of a double bond at the other end of B-ocimene. Placement of the other fragments to conform to the carbon skeleton yields the following structural formula for B-ocimene. 

The discovery of the Carroll reaction in 1940 allowed significant improvements to be made to Arens and van Dorp s synthesis. The Carroll reaction involves heating the acetoacetate ester of an allyl alcohol. The ester can be formed in situ from the alcohol and ethyl acetoacetate. The reaction is an electrocyclic one which results in the elimination of carbon dioxide and the addition of an acetone fragment to the terminal carbon of the double bond of the alcohol. The mechanism is shown in Figure 9.8. 

Fit a 750 ml. round-bottomed flask with a fractionating column attached to a condenser set for downward distillation. Place 500 g. of diacetone alcohol (the crude product is quite satisfactory), 01 g. of iodine and a few fragments of porous porcelain in the flask. Distil slowly. with a small free flame (best in an air bath) and collect the following fractions (a) 56-80° (acetone and a little mesityl oxide) (6) 80-126° (two layers, water and mesityl oxide) and (c) 126-131° (mesityl oxide). Whilst fraction (c) is distilling, separate the water from fraction (6), dry with anhydrous potassium carbonate or anhydrous magnesium sulphate, and fractionate from a small flask collect the mesityl oxide at 126-131°. The yield is about 400 g. 

Content of prime - tertiary peroxide groups was measured by the quantity of products of complete decay, which were measured by chromatography. It is known that the main contents in products of the complete decay of Oct-MA-TBPMM samples are acetone and 2,2-dimethylpropanol, which arise in reactions of chain fragmentation of tert-butylperoxy radical or in reaction of chain transfer of this radical. In this case the sum of acetone and 2,2-dimethylpropanol molecules is equal to the quantity of peroxide groups in polymer. As an internal standard we used chloroform. 

The mass spectra of methyl 3-deoxy-p-v-tkreo-pentopyrano-side, methyl 4-deoxy-j3-T>-thieo-pentopyranoside, and 5-deoxy-fi-D-xylo-furanoside are discussed and compared fragmentation paths are sufficiently different to allow identification on the basis of their mass spectra. On the other hand, the mass spectra of methyl 2- and 3-deoxy-5-O-methyl-f3-i>-erythro-pentofuranosides do not exhibit fragmentation differences. The mass spectra of 3-deoxy-l,2 5,6-di-O-isopropylidene -d-xylo - hexofuranose, 5- deoxy -1,2-0-isopropylidene-D-xy o-hexofuranose, and 6-deoxy-l,2-0-iso-propylidene-D-glucofuranose show prominent differences, even between the 5- and 6-deoxy isomers. The interpretation of the spectra was aided by metastable-ion peaks, mass spectra of DzO-exchanged analogs, and the mass spectrum of an O-isopropylidene derivative prepared with acetone-d6. 

Compound 10 was also prepared using acetone-d6 Peak shifts between the mass spectra of compounds 10 and 10a will be used to interpret the fragmentation of compound 10. 

The Mass Spectra of O-Isopropylidene Ketals 9 (Figure 6), 10, (Figure 7), and 11 (Figure 8). Three fragmentations characteristic of O-isopropylidene ketals are loss of a methyl radical from the ketal ring, cleavage of bonds adjacent to the ketal ring, and loss of acetone (12). 

In the mass spectrum (Figure 6) of 3-deoxy-l,2 5,6-di-0-isopropyli-dene-D-xt/Zo-hexofuranose (9) the fragmentations described above are found at m/e 229, 171, 143, 111, and 101. The fragments at m/e 143 and 101 arise by cleavage of C-4-C-5 with charge retention on C-4 and C-5, respectively (see Equations 17 and 18). Scheme 2 summarizes the losses of a methyl group, acetone from the second cyclic ketal function, and... 

Many radicals undergo fragmentation or rearrangement in competition with reaction with monomer. For example, f-butoxy radicals undergo p-scission to form methyl radicals and acetone (Scheme 3.6). 

An effective means to facilitate the mass-spectral analysis of rubber acetone extracts is to use desorp-tion/ionisation techniques, such as FD [92,113] and FAB [92]. FAB mass spectra for rubber extracts are generally more complex (due to fragment ions) than FD spectra of the same materials. Nevertheless, the FAB spectra are often complementary to FD, since ... 

Thermolytic processes are so far known to play only a minor role in the generation of the PO ion. An isolated case is the thermolysis of the monosodium salt of acetonylphosphonic acid at 150 °C, which leads to acetone and sodium polymetaphosphate 107). A cyclic fragmentation mechanism, as known for P-ketocarboxylic acids, could lead to PO in this case. 

---