Origins of thermodynamic stability of urea:alkane inclusion compounds

1998 ◽  
Vol 76 (11) ◽  
pp. 1695-1698 ◽  
Author(s):  
Mary Anne White
Keyword(s):  
Thermodynamic Stability ◽  
Inclusion Compounds ◽  
Solid Phase ◽  
Minor Role ◽  
Melting Points ◽  
Urea Inclusion Compounds ◽  
Guest Species ◽  
The Stability ◽  
A Minor ◽  
Urea Inclusion

Using existing thermodynamic data, the thermodynamic stabilities of urea inclusion compounds with three different alkane guests (decane, dodecane, and hexadecane) have been determined. In all cases the inclusion compounds are found to be thermodynamically stable with respect to their component species up to their melting points. From the present analysis, the solid-solid phase transitions are found to play only a minor role in stabilization, and the thermodynamic stability is found to be predominantly enthalpically driven. At a given temperature, the stability increases in the order urea:decane < urea:dodecane < urea:hexadecane. The present analysis shows that above the melting point of the guest species the inclusion compounds become much less stable because of the competition of the liquid guest. This destabilization eventually leads to incongruent melting.Key words: urea inclusion compounds, thermodynamic stability.

scholarly journals THERMAL DECOMPOSITION OF MOLECULAR COMPLEXES: III. UREA INCLUSION COMPOUNDS OF MONOSUBSTITUTED ALIPHATIC SERIES

1963 ◽  
Vol 41 (9) ◽  
pp. 2144-2153 ◽  
Author(s):  
H. G. McAdie
Keyword(s):  
Thermal Decomposition ◽  
Inclusion Compounds ◽  
Guest Molecule ◽  
Molecular Complexes ◽  
Decomposition Temperature ◽  
Urea Inclusion Compounds ◽  
Guest Species ◽  
Alkyl Bromides ◽  
Sufficient Energy ◽  
Urea Inclusion

Examination of the thermal decomposition of urea inclusion compounds has been extended to complexes of the even-numbered members of the following aliphatic series: n-alcohols, n-alkylamines, n-alkyl bromides, and n-carboxylic acids. The decomposition has been studied primarily by differential thermal analysis and an attempt made to correlate the observed decomposition temperatures and heats of decomposition with the particular guest species. The decomposition mechanism appears to involve acquisition of sufficient energy by the guest molecule to permit its diffusion from the canal, the decomposition temperature being related to the activation energy required for this diffusion process.

UREA INCLUSION COMPOUNDS OF n-ALKYL BROMIDES AND IODIDES

1964 ◽  
Vol 42 (5) ◽  
pp. 1069-1072 ◽  
Author(s):  
Jack Radell ◽  
B. W. Brodman ◽  
E. D. Bergmann
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Inclusion Compounds ◽  
Powder Diffraction Data ◽  
Cross Sectional ◽  
X Ray ◽  
Urea Inclusion Compounds ◽  
Alkyl Bromides ◽  
The Stability ◽  
Urea Inclusion

The formation and stability of urea inclusion compounds of n-alkyl bromides and iodides were established from X-ray powder diffraction data. The stability of both homologous families is greater than would be expected from a consideration of the cross-sectional diameter of the molecules only. The procedure for isolating the complexes has been simplified.

Extraction of strontium and barium salts by the nitrobenzene solution of dicarbolide in the presence of glymes

1985 ◽  
Vol 50 (3) ◽  
pp. 581-599 ◽  
Author(s):  
Petr Vaňura ◽  
Emanuel Makrlík
Keyword(s):  
Stability Constants ◽  
Organic Phase ◽  
Equilibrium Constants ◽  
Minor Role ◽  
Nitrobenzene Solution ◽  
Ligand Structure ◽  
Stability Constants Of Complexes ◽  
Separation Factors ◽  
The Stability ◽  
A Minor

Extraction of microamounts of Sr2+ and Ba2+ (henceforth M2+) from the aqueous solutions of perchloric acid (0.0125-1.02 mol/l) by means of the nitrobenzene solutions of dicarbolide (0.004-0.05 mol/l of H+{Co(C2B9H11)2}-) was studied in the presence of monoglyme (only Ba2+), diglyme, triglyme, and tetraglyme (CH3O-(CH2-CH2O)nCH3, where n = 1, 2, 3, 4). The distribution of glyme betweeen the aqueous and organic phases, the extraction of the protonized glyme molecule HL+ together with the extraction of M2+ ion and of the glyme complex with the M2+ ion, i.e., ML2+ (where L is the molecule of glyme), were found to be the dominating reactions in the systems under study. In the systems with tri- and tetraglymes the extraction of H+ and M2+ ions solvated with two glyme molecules, i.e., the formation of HL2+ and ML22+ species, can probably play a minor role. The values of the respective equilibrium constants, of the stability constants of complexes formed in the organic phase, and the theoretical separation factors αBa/Sr were determined. The effect of the ligand structure on the values of extraction and stability constants in the organic phase is discussed.

Structural properties of the guest species in diacyl peroxide/urea inclusion compounds: an X-ray diffraction investigation

1990 ◽  
Vol 431 (1882) ◽  
pp. 245-269 ◽  
Keyword(s):  
Single Crystal ◽  
Structural Properties ◽  
Inclusion Compounds ◽  
X Ray Diffraction ◽  
Channel Axis ◽  
Guest Molecules ◽  
X Ray ◽  
Urea Inclusion Compounds ◽  
Diacyl Peroxide ◽  
Urea Inclusion

In this paper we report single crystal X-ray diffraction studies of urea inclusion compounds containing diacyl peroxides (dioctanoyl peroxide (OP), diundecanoyl peroxide (UP), lauroyl peroxide (LP)) as the guest component. In these inclusion compounds, the host (urea) molecules crystallize in a hexagonal structure that contains linear, parallel, non-intersecting channels (tunnels). The guest (diacyl peroxide) molecules are closely packed inside these channels with a periodic repeat distance that is incommensurate with the period of the host structure along the channel axis. Furthermore, there is pronounced inhomogeneity within the guest structure: within each single crystal, there are regions in which the guest molecules are three-dimensionally ordered, and other regions in which they are only one-dimensionally ordered (along the channel axis). Although it has not proven possible to ‘determine’ the guest structures in the conventional sense, substantial information concerning their average periodicities and their orientational relationships with respect to the host has been deduced from single crystal X-ray diffraction photographs recorded at room temperature. For OP/urea, UP/urea and LP/urea, the guest structure in the three-dimensionally ordered regions is monoclinic, and six types of domain of this monoclinic structure can be identified within each single crystal. The relative packing of diacyl peroxide molecules is the same in each domain, and the different domains are related by 60° rotation about the channel axis. For each of these inclusion compounds, the offset between the ‘heights’ of the guest molecules in adjacent channels is the same ( ca . 4.6 Å (4.6 x 10 -10 m)) within experimental error, suggesting that the relative interchannel packing of the guest molecules is controlled by a property of the diacyl peroxide group. In addition to revealing these novel structural properties, the work discussed in this paper has more general relevance concerning the measurement and interpretation of single crystal X-ray diffraction patterns that are based on more than one three-dimensionally periodic reciprocal lattice. Seven separate reciprocal lattices are required to rationalize the complete X-ray diffraction pattern from each diacyl peroxide/urea crystal studied here.

Urea inclusion compounds of n-alkyl oxiranes and n-mercaptans

Tetrahedron ◽  
1963 ◽  
Vol 19 (6) ◽  
pp. 873-877
Author(s):  
J. Radell ◽  
B.W. Brodman ◽  
E.D. Bergmann
Keyword(s):  
Inclusion Compounds ◽  
Urea Inclusion Compounds ◽  
Urea Inclusion

scholarly journals The true structural periodicities and superspace group descriptions of the prototypical incommensurate composite materials: Alkane/urea inclusion compounds

2016 ◽  
Vol 116 (5) ◽  
pp. 56001 ◽  
Author(s):  
Michel Couzi ◽  
François Guillaume ◽  
Kenneth D. M. Harris ◽  
Benjamin A. Palmer ◽  
Kirsten Christensen ◽  
...  
Keyword(s):  
Composite Materials ◽  
Inclusion Compounds ◽  
Urea Inclusion Compounds ◽  
Urea Inclusion
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