engleski

2-Benzyl-1,3-diphenyl-1,3-propanedione and 4-Benzyl-2,2,6,6-tetramethyl-3,5-heptanedione

Special properties of material are related to the fine interactions between its units on the molecular level. Predicting the properties of a compound strives for better understanding of the rules determining the inception of crystallization and the course of crystal growth especially when the strongest intermolecular attractions are those of the hydrogen bond type. Although these interactions should have the strongest influence to the packing of the molecules, the conditions in which the dispersion of the energy takes place with the greatest extent must not be neglected. It depends largely on the contact surface and it is dominantly determined by the actual shape of the molecule. We began to investigate this influence on a series of simple Calpha mono- and dibenzyl substituted beta-diketones with the same central O-Csp2-Ca-Csp2-O molecular core differentiating in the terminal groups only. The difference in the crystal and molecular structure could be caused by the specific properties of the terminal groups including shape, bulkiness and the electronic structure. Crystal data. (I) C22H18O2, Mr = 314.38, monoclinic, space group P 21/n, a = 10.294(1) A,b = 10.906(1) A, c = 15.409(1) A, beta = 98.56(1) °, V = 1710.5(2) A3, Z = 4, Dc = 1.22 g cm-3, F(000) = 664, lambda(MoKa) = 0.71073 A, mi(MoKa) = 0.07 mm-1, R = 0.049, wR = 0.083 for 2426 (Inet gt 2sInet) out of the 3733 reflections and 217 variable parameters. (II) C18H26O2,Mr = 274.4, monoclinic, space group P 21/n, a = 16.971(1) A, b = 5.915(1) A, c = 18.269(1) A, beta = 111.26(1) °, V = 1708.9(3) A3, Z = 4, Dc = 1.07 g cm-3, F(000) = 600, lambda(MoKa) = 0.71073 A, mi(MoKa) = 0.06 mm-1, R = 0.055, wR = 0.083 for 1232 (Inet gt 2sInet) out of the 3728 reflections and 181 variable parameters. The crystals of both compounds are built up of diketo tautomeric molecules having distorted U conformation. The differentiating terminal residues in (II) [two t-butyl versus two benzyl radicals in (I)] did not affect the stereochemistry of the central moiety of the molecules at all. The deviation of oxygen atoms from the plane made up of three central carbon atom Csp2-Ca-Csp2 is essentially identical in both compounds [0.461(8) and 1.053(7) A in (I); 0.457(5) and 1.054(3) A in (II)]. The crystal structure of (I) is dominated by an intramolecular and an intermolecular C-HˇˇˇO hydrogen bond (2.799 and 2.897 A, respectively). The crystal structure of II contains just an intramolecular C-HˇˇˇO contact of similar value (2.771 A). Characterization and the determination of physical and chemical properties were accomplished by the MS, 1H and 13C NMR, FT IR, DSC and X-ray structure analysis.

Diketones; tautomerism; crystal structure

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