Acetone molecular shape

Acetone and 2-methylpropane have similar molecular shapes, but acetone has a large dipole moment resulting from its polar CDO bond. 

However, dendrimeric and hyperbranched polyesters are more soluble than the linear ones (respectively 1.05, 0.70, and 0.02 g/mL in acetone). The solution behavior has been investigated, and in the case of aromatic hyperbranched polyesters,84 a very low a-value of the Mark-Houvink-Sakurada equation 0/ = KMa) and low intrinsic viscosity were observed. Frechet presented a description of the intrinsic viscosity as a function of the molar mass85 for different architectures The hyperbranched macromolecules show a nonlinear variation for low molecular weight and a bell-shaped curve is observed in the case of dendrimers (Fig. 5.18). 

Figure 5 (a)-(c) shows the absorption spectra of some halogenated ketones in the near ultraviolet. In the case of acetone itself the absorption may be attributed to an n - tt transition associated with the carbonyl group. The substitution of halogen atoms leads to an increase in the molecular extinction coefficient and a shift of the absorption maximum toward the red. The ketones containing both chlorine and fluorine atoms show absorption curves with some fine structure but it is not possible to find any correlation between the structure and the shape of the absorption curve. 

In Fig. 5b, which was obtained at 30°C, the powder pattern displays a severely distorted, intermediate rate line shape. This line shape is characteristic of both fast methyl group rotation and 2 fold molecular re-orientation about the carbonyl bond at a rate comparable to the reciprocal of the quadrupolar coupling constant ( 105 Hz). At room temperature, therefore, the acetone-d6 molecules in the microporous channels of sepiolite are able to undergo restricted re-orientations. 

As shown in Figure 42 for the Norrish II reactions of a simple ketone, 2-nonanone, not only do the shapes of the products differ from those of the reactant, but so do their molecular volumes [265]. Interestingly, the volume of the fragmentation products, 1-hexene and 2-hydroxypropene (which ketonizes to acetone), are closer in volume to 2-nonanone than is either of the cyclization products. They are also capable of occupying more efficiently the shape allocated by a stiff solvent matrix to a molecule of 2-nonanone in its extended conformation the cross-sectional diameter of either of the cyclobutanols is much larger than that of extended 2-nonanone or the fragmentation products when spaced end-on. Both of these considerations should favor fragmentation processes if isomorphous substitution for the precursor ketone in the reaction cavity is an important requirement for efficient conversion to photoproducts. 

However, a positive proof for hula-twist could not be obtained by X-ray diffraction, as the product phase became amorphous. The external shape of the crystal did not change at the microscopic level, but AFM indicated some loss of acetone on (100) by efflorescence, forming a protective cover which can be correlated with the crystal packing. Further molecular migrations on other faces were not detected with the molecular sensitivity of AFM [6], The crystal stayed clear transparent, but a topotactic conversion is excluded if a crystalline phase becomes an amorphous product phase. 

For the first time we report the synthesis of macrocycles like calixpyrrole, cyclotriveratrylene (CTV), cyclotetraveratrylene (CTTV), porphyrine ete over molecular sieve as a catalyst. Calixpyrroles are synthesized from pyrrole and a ketone like acetone over MCM-41 under reflux conditions using suitable solvent. In case of MCM-41 cyclic calixpyrroles were obtained. On the other hand due to shape selectivity in case of Y zeolite linear di-, tri- and tetra- polypyrroles were obtained and cyclic tetramers were not observed. The mechanism of the synthesis of calixpyrrole is either by the dimerization of dimer with simultaneous cyclization to cyclic tetramer or cyclization of linear tetramer via recoil phenomenon. 

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