Urea and Thiourea Adduction of C<sub>5</sub>—C<sub>42</sub>-Hydrocarbons

Schiessler, Robert W.; Flitter, David

doi:10.1021/ja01127a033

Cited by 102 publications

(31 citation statements)

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“…Thiourea, in a similar way, combines with several substrates to form non-stoichiometric complexes analogous to the urea inclusion complexes. [3][4][5][6]12] By contrast, we are unaware of inclusion complexes in which N-alkyl or N,N'-dialkyl ureas serve as the hosts. However, N,N'-disubstituted ureas, in which the substituents are more complex than an n-alkyl chain, can form a-networks (i.e., with one degree of translational symmetry [13] ), [14,15] and some of these have been shown to lead to gels [16,17] with organic liquids and water.…”

Section: Introductionmentioning

confidence: 99%

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Urea and Thiourea Derivatives as Low Molecular‐Mass Organogelators

George

Tan

John

et al. 2005

Chemistry A European J

166

108

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The properties of a series of organogels consisting of a urea or thiourea derivative with one or two n-alkyl substitutuents at the nitrogen atoms (a low molecular-mass organogelator (LMOG)) and an organic liquid are described. They include N,N'-dimethylurea, the LMOG of lowest molecular mass (M(W) 88) we are aware of. The efficiencies of the LMOGs, based the diversity of liquids gelated, the minimum amount required for gelation of a liquid at room temperature, and the temporal and thermal stabilities of the gels formed, have been investigated as a function of the number, length, and substitution pattern of their n-alkyl chains. The gels are thermally reversible and require generally very low concentrations (<2 wt %) of an LMOG. Some of the LMOGs with shorter chains are more efficient than their longer chained analogues. The structural and thermodynamic properties of the gels have been examined by IR, DSC, and X-ray diffraction techniques. Polarizing optical microscopic analyses of the gels show that the nature of gelator aggregates depends mainly on the alkyl chain length. Changes in the aggregation ability have been examined systematically by perturbing the molecular structure.

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Section: Introductionmentioning

confidence: 99%

“…[1,2] It is known to form inclusion complexes with n-alkanes (! 7 carbon atoms) [3][4][5][6] and some functionalized longchain molecules. [3,[7][8][9][10][11] In these complexes, the urea molecules self-assemble through intermolecular hydrogen bonds and orient in a helical lattice into which the guest molecules fit.…”

Section: Introductionmentioning

confidence: 99%

Urea and Thiourea Derivatives as Low Molecular‐Mass Organogelators

George

Tan

John

et al. 2005

Chemistry A European J

166

108

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“…Our inspiration for using ureas in self-assembly was drawn from urea itself, which can assemble in the solid state into cylinders, having an alkyl chain threaded through its center (15,16). Furthermore, the hydrogen-bonding propensities of ureas have been extensively studied (17,18).…”

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confidence: 99%

Synthesis and assembly of self-complementary calix[4]arenes.

Shimizu

Rebek

1995

Proc. Natl. Acad. Sci. U.S.A.

283

138

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A calix [4]arene was designed to reversibly dimerize and form an egg-shaped enclosure. Adhesive interactions in the assembly were provided by four self-associating ureas, which form a cyclic array containing 16 hydrogen bonds. The synthesis was completed in four steps from theEvidence for dimerization of the calixarene tetraurea was provided by 'H NMR, mass spectrometry, and the observation of encapsulated molecules. The resulting cavity was of sufficient size to capture guests such as ethyl benzene andp-xylene.

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“…Urea and thiourea [46,47] adduction is a particularly useful method for separating n-and isoalkanes, although certain aromatics [48] and naphthenes will also complex with thiourea. The molecular types which form adducts are listed by McLAUGHLIN [49].…”

Section: Separation Techniquesmentioning

confidence: 99%