Isomorphism and mixed crystals in 2-R-naphthalenes: evidence of structural subfamilies and prediction of metastable forms

Abstract

Solid±liquid binary phase diagrams and isothermal unitcell parameters as a function of composition are given for the high-temperature form (P2 1 /a, Z = 2) mixed crystals generated by 2-¯uoronaphthalene, naphthalene and 2-naphthol with four other derivatives of naphthalene. The study leads to the distinction between two high-temperature forms (or types of packing). The ®rst one (type 1) is taken by ®ve 2-R-naphthalenes (R = F, Cl, Br, SH, CH 3 ; the ®rst subfamily), the second one (type 2) by naphthalene itself and 2-naphthol (R = H, OH; the second subfamily). The crystallographic data also allow an estimation of unit-cell parameters for the metastable forms of naphthalene (type 1, a = 8.0, b = 5.95, c = 8.6 A Ê , = 116) and 2-¯uoronaphthalene (type 2, a = 8.336, b = 5.915, c = 9.000 A Ê , = 122.23 ), supporting an interpretation, in terms of crossed isodimorphism, of the observed two-phase regions in systems in which the components do not belong to the same subfamily.

The Two-Component System CCl4 + CBrCl3. Inference of the Lattice Symmetry of Phase II of CBrCl3

“…Accordingly, this value should correspond to the well-known manifestation of a similarity between the host and guest molecules as well as the intermolecular interactions (taking into consideration that excess enthalpy seems to be small, see Figure ) and the additional disorder introduced by the substitution process. It has been well established that, for mixed crystals formed between compounds in which orientational and translational long-range order exists, the molecular symmetry appears to be of crucial importance. , If the steric conditions permit the molecular substitution of the guest molecule in the host lattice and the guest molecule does not display the required symmetry elements of the host lattice site, a symmetry simulation must be generated by the appearance of an orientational disorder or by a change of the occupancy of the sites when the molecules are very close in shape. This obvious requirement has been argued to explain the large miscibility in the OD phases. − For the analyzed monoclinic mixed crystals, although the molecular symmetry of the CCl 4 molecules ( T d ) is higher than that of the CBrCl 3 molecules ( C 3 v ), the T d symmetry should be fulfilled by the latter, because the lattice symmetry of both monoclinic phases of pure compounds have been found to be one and the same ( C 2/ c ).…”

Novel Solid Solution of the Antiretroviral Drugs Lamivudine and Emtricitabine

“…11,18 Despite the fact that FTC has an extremely similar molecular structure to 3TC, differing by a single fluorine atom at the C5 position of the aromatic ring (Figure 1), just one crystalline structure of the former was reported. 17 Examples of organic mixed crystals can be seen in the 2-Rnaphthalenes family, 19 omeprazole tautomeric forms, 9 and benzylidenecyclopentane derivatives, 7 and they generally present isomorphous constituents. Nonetheless, several solid solutions of nonisostructural crystals have also been previously reported.…”

“…Examples of organic mixed crystals can be seen in the 2- R -naphthalenes family, omeprazole tautomeric forms, and benzylidenecyclopentane derivatives, and they generally present isomorphous constituents. Nonetheless, several solid solutions of nonisostructural crystals have also been previously reported. , In this work, we report the unprecedented crystalline structure of the solid solution between two APIs: 3TC and FTC.…”

Modelling Phase Equilibria in Systems with Organic Solid Solutions

“…Reports on the formation of alloys, or solid solutions, of organic compounds, although still rare, have been appearing regularly in the last few years for aromatic compounds, such as substituted benzenes and naphtalenes [1][2][3], pyrene and anthracene [4][5][6], for carbohydrates [7], terpenes [8], neopentane derivatives [9-10] and fulerenes, besides solid solutions of C 60 with C 70 [11][12] solid solutions of C 60 in sulphur have been reported [13]. Nevertheless it is among the molecules with long n-alkyl chains such as n-alcohols Although the materials based on n-alkane alloys have been used for long as candles, waterproof coatings, pharmaceutical and cosmetics, and in spite of paraffin waxes being a valuable by-product of petroleum refining, the research on n-alkane solid solutions has been mainly prompted by its dark side: The damages and losses caused by wax precipitation from petroleum fluids.…”

“…Reports on the formation of alloys, or solid solutions, of organic compounds, although still rare, have been appearing regularly in the last few years for aromatic compounds, such as substituted benzenes and naphtalenes [1][2][3], pyrene and anthracene [4][5][6], for carbohydrates [7], terpenes [8], neopentane derivatives [9][10] and fulerenes, besides solid solutions of C 60 with C 70 [11][12] solid solutions of C 60 in sulphur have been reported [13]. Nevertheless it is among the molecules with long n-alkyl chains such as n-alcohols [14], fats [15], soaps [16] and alkanes [17][18][19][20] that solid solutions appear more frequently.…”