Dilactones 2 molecules

Molecules in real solvents can exist in one or more tautomeric forms. The use of different tautomers in calculations can lead to significant variation in the estimated log P values (Pig. 15.1). Accurate prediction of the dominant tautomer requires ah initio calculahons. Due to speed limitations such calculations are not feasible for virtual screening and prediction of large compound collections. Moreover, the interpretation of the results can also be difficult, for example, the lacton-lactim (Pig. 15. IB) is the stable form of maleic hydrazide in the gas phase but the difference between this and the dilacton form (Pig. 15.1C and D) disappears in solution... 

The dilactone 6 dihydrate isolated from hexane has a melting point of 65-66 °C. At 60° in vacuo the waters of hydration are lost, and the anhydrous compound melts at 83-84 °C. In the dihydrate the donor centers lie within 0,26 A of the mean plane. One water molecule coordinates directly with the host and lies 0.14(9) A below the plane, 0 -0(4) = 2.92 A (Fig. 33). The pyridino nitrogen, which usually functions as a donor atom, does not participate in the binding of the water. The second water molecule is hydrogen bonded to the first (0- 0 = 3.01 A), and does not interact significantly with the crown ether. 

Tannins Gallic acid 45 is a phenolic compound found mainly in grape seeds and stems, but also it can be leached from oak barrels, occurring generally in amounts of 10-100mg/L. Two molecules of gallic acid in a head-to-tail fashion are the dilactone ellagic acid 46 ... 

Because of the exposure to light the Cl-atom must have been cleaved and a five membered lactone and/or dilactone ring formed which prevented the penetration of solvent molecules inside the polymer matrix. Formation of lactone rings was confirmed by taking IR spectrum of a sunlight-exposed and of a thermally treated sample. 

Draw a structural formula of the polymer resulting from base-catalyzed polymerization of each compound. Would you expect the polymers to be optically active (S)-(+)-lactide is the dilactone formed from two molecules of (S)-(+)-lactic acid. 

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