Search tips
Search criteria

Results 1-3 (3)

Clipboard (0)
Year of Publication
Document Types
1.  Polymorphism and phase transition behavior of 6,6′-bis­(chloro­meth­yl)-1,1′,4,4′-tetra­methyl-3,3′-(p-phenyl­enedimethyl­ene)bis­(piperazine-2,5-dione) 
A crystallographic investigation of the title compound, C22H28Cl2N4O4, using crystals obtained under different crystallization conditions, revealed the presence of two distinct polymorphic forms. The mol­ecular conformation in the two polymorphs is very different: one adopts a ‘C’ shape, whereas the other adopts an ‘S’ shape. In the latter, the molecule lies across a crystallographic twofold axis. The ‘S’-shaped polymorph undergoes a reversible ortho­rhom­bic-to-monoclinic phase transition on cooling, whereas the structure of the ‘C’-shaped polymorph is temperature insensitive.
PMCID: PMC2720150  PMID: 19652319
2.  3-[1-(4-Sulfamoylphen­yl)-5-p-tolyl-1H-pyrazol-3-yl]propanoic acid and 3-[5-(4-bromo­phen­yl)-1-(4-sulfamoyl­phen­yl)-1H-pyrazol-3-yl]­propanoic acid–dichloro­methane–diethyl ether–water (2/0.72/1/1) 
The syntheses of 3-[1-(4-sulfamoylphenyl)-5-p-tolyl-1H-pyra­zol-3-yl]propanoic acid, C19H19N3O4S, (I), and 3-[5-(4-bromo­phen­yl)-1-(4-sulfamoyl­phen­yl)-1H-pyrazol-3-yl]­propanoic acid–dichloro­methane–diethyl ether–water (2/0.72/1/1), 2C18H16BrN3O4S·0.72CH2Cl2·C4H10O·H2O, (II), are regio­specific. However, correct identification by spectroscopic techniques of the regioisomer formed is not trivial and single-crystal X-ray analysis provided the only means of unambiguous structure determination. Both structures make extensive use of hydrogen bonding and while compound (I) forms a straightforward unsolvated Z′ = 1 structure, compound (II) crystallizes as an unusual mixed solvate, with two crystallographically unique mol­ecules of the pyrazole derivative present in the asymmetric unit. The structure of (II) also features Br⋯Br inter­actions.
PMCID: PMC2724996  PMID: 19498242
3.  3-[5-(4-Chloro­phen­yl)-1-(4-methoxy­phen­yl)-1H-pyrazol-3-yl]propionic acid and the corresponding methyl ester 
The synthesis of 3-[5-(4-chloro­phen­yl)-1-(4-methoxy­phen­yl)-1H-pyrazol-3-yl]propionic acid, C19H17ClN2O3, (I), and its corresponding methyl ester, methyl 3-[5-(4-chloro­phen­yl)-1-(4-methoxy­phen­yl)-1H-pyrazol-3-yl]propionate, C20H19ClN2O3, (II), is regiospecific. However, correct identification of the regioisomer formed by spectroscopic techniques is not trivial and single-crystal X-ray analysis provided the only means of unambiguous structure determination. Compound (I) crystallizes with Z′ = 2. The propionic acid groups of the two crystallographically unique mol­ecules form a hydrogen-bonded dimer, as is typical of carboxylic acid groups in the solid state. Conformational differences between the meth­oxy­benzene and pyrazole rings give rise to two unique mol­ecules. The structure of (II) features just one mol­ecule in the asymmetric unit and the crystal packing makes greater use than (I) of weak C—H⋯A inter­actions, despite the lack of any functional groups for classical hydrogen bonding.
PMCID: PMC2724994  PMID: 19346614

Results 1-3 (3)