Group carbonyls, physical properties

Polyesters are another important class of polyols. There are many polyester types used, so a generic structure is shown in Scheme 4.4. They are often based on adipic acid and either ethylene glycol (ethylene adipates) or 1,4-butanediol (butylene adipates). Polyesters, because of the polar carbonyl groups, contribute more to intermolecular forces, and physical properties such as tear and impact resistance are often improved by using them. They are also utilized for their solvent and acid resistance and light stability. Relatively poor hydrolytic stability is... 

The structure of the labile intermediate compound "Y" is uncertain. On the basis of its physical properties and chemical behaviour (which cannot be detailed here), possible formulations that were originally (485) considered included a six-membered bridged carbonyl-structure, as well as seven- or five-membered rings. The Italian group of workers (536) favoured the seven-membered ring-structure (CXVI) for the intermediate "Y", and 5-phenylguanamine structures (CXXI) for the final stable products. 

Physical properties depend upon the same types of steric effects as chemical reactivities. In both types of data the measurable phenomenon is occurring at a clearly defined active site. Thus, for the ionization of a set of phenols the active site is the OH group, while for the stretching frequency in the infrared spectrum of the acetyl group in a set of acetophenones the active site is the carbonyl group. In the case of bioactivities, steric effects in the formation of the bioactive substance-receptor site complex are frequently of great importance. In this case the entire bioactive... 

The polarity of the carbonyl group is manifest in the physical properties of carbonyl compounds. Boiling points for the lower members of a series of aldehydes and ketones are 50-80° higher than for hydrocarbons of the same molecular weight this may be seen by comparing the data of Table 16-2 (physical... 

Laurence51 has derived cr/ values (he uses the symbol correlation analysis of the carbonyl stretching frequencies of 4-substituted camphors in carbon tetrachloride. The value of 0.11 is given for the vinyl group, in good agreement with the reactivity-based values discussed above, in spite of the use of a non-polar medium. Laurence compares this with a statistical value of 0.06 from Taft and Topsom57, said to refer to effects on physical properties in either the gas phase or in hydrocarbon or similar solvents. 

The carbonyl group is polarised in such a way that the oxygen is slightly negative and the carbon is slightly positive. Both the polarity of the carbonyl group and the presence of the weak n bond explain much of the chemistry and the physical properties of aldehydes and ketones. The polarity of the bond also means that the carbonyl group has a resultant dipole moment. 

Nearby elements also display chemistry reflecting alkyne 7rx donation to a vacant metal dir orbital. In Group V, Lippard s coupled carbonyl product Ta(Me3SiOC=COSiMe3)(dmpe)2Cl is a d4 Ta(I) alkyne monomer (116), similar in electron count to CpV(CO)2(RC=CR) complexes (231). The preparative route and physical properties of a series of Ta(CO)2-(RC=CR)(I)L2 d4 monomers are compatible with a four-electron donor description for the alkyne ligands (231a). The d2 configuration has also... 

Structure of the Carbonyl Group 817 18-3 Nomenclature of Ketones and Aldehydes 818 18-4 Physical Properties of Ketones and Aldehydes 820 18-5 Spectroscopy of Ketones and Aldehydes 822 18-6 Industrial Importance of Ketones and Aldehydes 828 18-7 Review of Syntheses of Ketones and Aldehydes 829 18-8 Synthesis of Ketones from Carboxylic Acids 833 18-9 Synthesis of Ketones and Aldehydes from Nitriles 833... 

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