The molecular structure of diphenylmethyl methacrylate

The molecular structure of diphenylmethyl methacrylate has been determined by means of X-ray diffraction. Crystals are monoclinic, space group C2/c, a = 29, 177 (2), b = 6,017(1), c = 16,110(1) Å, β = 96,840(5)°, and Z = 8. The structure was solved by the direct method and refined by the block-diagonal least-squares procedure to R = 0,071 (R_w = 0,091) for 1768 measured reflections. The molecule has an antiperiplanar conformation as to the C?C and C?O double bonds about the C(1)? C(2) bond and a synperiplanar conformation as to the C?O and C? O bonds about C(1)? O(1).     

The molecular structures of (RS)-1,2-diphenylethyl methacrylate and (RS)-α-tert-butylbenzyl methacrylate

The molecular structures of (RS)-1,2-diphenylethyl methacrylate (DPEMA) and (RS)-α-tert-butylbenzyl methacrylate (t-BBMA) were determined by means of X-ray diffraction. Crystals of (RS)-DPEMA are monoclinic, space group C2/c, a = 33,341(3), b = 5,916(1), c = 15,911(2) Å, β = 106,42(1)°, and Z = 8. Crystals of (RS)-t-BBMA are also monoclinic, space group P2₁/c, a = 6,028(1), b = 31,009(3), c = 15,207(1) Å, β = 96,780(8)°, and Z = 8. Both structures were solved by the direct method and refined by the block-diagonal least-squares procedure: DPEMA, R = 0,113 for 1 100 observed reflections and t-BBMA, R = 0,081 for 2206 non-zero reflections, respectively. The molecule of DPEMA has an antiperiplanar conformation as to the C?C and C?O double bonds about the C(1)? C(2) bond, a synperiplanar conformation as to the C?O and C? O bond about the C(1)? O(1) bond, and an anticlinal conformation about the O(1)? C(5) bond. One of the two t-BBMA molecules in an asymmetric unit has an antiperiplanar conformation as to the C?C and C?O double bonds about the C(1)? C(2) bond, whereas the other antiperiplanar molecule may contain some synperiplanar conformation. Both molecules have a synperiplanar conformation as to the C?O and C? O bonds about the C(1)? O(1) bond and an anticlinal conformation about the O(1)? C(5).     

The molecular structures of methacrylates with bulky ester substituents, (RS)-1,2,2,2-tetraphenylethyl methacrylate and (1S, 2R)-(+)-1-benzyl-3-dimethylamino-2-methyl-1-phenylpropyl methacrylate

The molecular structures of (RS)-1,2,2,2-tetraphenylethyl methacrylate (TrBzMA) and (1S, 2R)-(+)-1-benzyl-3-dimethylamino-2-methyl-1-phenylpropyl methacrylate (ChMA) were determined by means of X-ray diffraction: (RS)-TrBzMA .0,5C₆H₆; triclinic, space group P1, a = 9,271(2), b = 33,965(4), c = 9,167(2) Å, α = 90,26(2), β = 118,80(2), γ = 88,03(2)°, and Z = 4; ChMA; monoclinic, space group P2₁, a = 12,482(1), b = 9,184(1), c = 9,246(1) Å, β = 93,49(1)°, and Z = 2. Both structures were solved by the direct method and refined by the block-diagonal least-squares procedure to R = 0,054 and 0,057 for non-zero reflections, respectively. Both of the two crystallographically independent molecules of TrBzMA have the same structure; each molecule has a synperiplanar (sp) conformation as to the C?C and C?O double bonds about the C(1)? C(2) bond and also an sp conformation as to the C?O and C? O bonds about the C(1)? O(1) bond. The ChMA molecule has an antiperiplanar (ap) and a sp conformation about the C(1)? C(2) and C(1)? O(1) bonds, respectively.     

4-(α,α-dimethylbenzyl)phenyl methacrylate, 1. Synthesis and crystal structure

4-(α,α-dimethylbenzyl)phenyl methacrylate ( 1 ) was prepared by reaction of 4-(α,α-dimethylbenzyl)phenol and methacryloyl chloride in ether. By careful crystallization from ether large monoclinic crystals could be obtained with the following crystal data: a = 6,622 (2) Å, b = 12,578 (2) Å, c = 9,892 (3) Å, β = 99,86° (3), D_c = 1,147 g · cm^?3, V = 811,1 ų, M = 280,4, λ = 0,7107 Å, μ = (Mo K_α) = 0,7 cm^?1, F(000) = 300, space group P2₁, Z = 2. Attempts to polymerize the monomer (m.p. 46–48°C) by γ-irradiation at ambient temperature gave only a small amount of a crosslinked product.     

The molecular structure of 4-(dimethylmaleimido)phenyl methacrylate

The molecular structure of 4-(dimethylmaleimido)phenyl methacrylate was determined by means of X-ray diffraction. Crystals are orthorhombic, space group F2dd, a = 3,993(1) Å, b = 36,650(6) Å, c = 39,460(8) Å and Z = 16; d_calc = 1,360 g · cm^?3, V = 5774,7 ų, M = 285,3, λ = 0,7107 Å, μ (MoK_α) = 1,06 cm^?1, F(000) = 2400. The structure was solved by direct methods and refined to R = 0,062 for 304 observed reflections. The molecule has a synperiplanar conformation as to the C?C and C?O double bonds about C(7)? C(8) and also as to the C?O and C? O bonds about C(7)? O(1).     

Structural study of compounds modelling elementary polymer units, 5. Molecular and crystal structures of C,C′-disubstituted o-carboranes

With the aim to determine the main structural characteristics of amorphous (branched and different-unit) polymers of the polyphenylene type, prepared by polycyclocondensation of carborane-containing mono- and diacetylaromatic compounds, an X-ray structural study of four model compounds was carried out, viz. of 1,2-bis[4-(4-acetylphenoxy)phenyl]-1,2-dicarba-closo-dodecaborane(12) ( 1 ) (triclinic crystals, a = 8,205 Å, b = 13,505 Å, c = 14,019 Å, α = 90,44°, β = 97,08°, γ = 97,24°, space group P1 , Z = 2, R = 0,045 for 2663 reflections), 1,2-bis(4-phenoxyphenyl)-1,2-dicarba-closo-dodecaborane(12) ( 2 ) (monoclinic crystals, a = 14,813 Å, b = 17,133 Å, c = 11,211 Å, β = 112,43°, space group P2₁/c, Z = 4, R = 0,066 for 3 286 reflections), 1,2-bis(4′-acetylbiphenyl-4-yl)-1,2-dicarba-closo-dodecaborane(12) ( 3 ) (orthorhombic crystals, at ?120°C a = 13,405 Å, b = 9,276 Å, c = 22,86 Å, space group Pnam, Z = 4 molecules on the m plane, R = 0,039 for 1 147 reflections), and 1,2-bis(4-acetylbenzyl)-1,2-dicarba-closo-dodecaborane(12) ( 4 ) (orthorhombic crystals, at ?120°C a = 22,03 Å, b = 26,23 Å, c = 8,026 Å, space group Fdd2, Z = 8 molecules lie on the two-fold axis, R = 0,051 for 577 reflections). The strained structure of the C,C′-o-diphenyl-substituted carboranyl fragment is established, the high conformational flexibility of 4-phenoxyphenyl linkages is confirmed and a tendency toward separate autoassociation of acetyl-containing polar groups and carborane nuclei is shown, with the autoassociation of polar groups completely suppressing that of carborane nuclei in case of conformational rigidity and shortness of the arylene linkages. These and other structural characteristics of the investigated model compounds and their crystals, in case they turn out to be characteristic also for the corresponding polymers and their precursors, should largely determine the structure and physico-chemical properties of their corresponding polymers.     

Crystal and molecular structure of a new spiro phosphorane monomer, 7-oxo-5-phenyl-5λ5-phospha-1,4,6-trioxaspiro[4.4]nonane

7-oxo-5-phenyl-5λ-⁵-phospha-1,4,6-trioxaspiro[4.4]nonane ( 3a ) (C₁₁H₁₃O₄P, monoclinic, P2₁/n, a = 14,751(2), b = 5,577(1), c = 14,490(3) Å, β = 106,91(2)°, V = 1140,5 ų, D_x(Z = 4) = 1,398 g · cm^?3, MW = 240,20, mp = 80°C) forms hygroscopic white needle-like crystals. The structure was solved by direct methods and the final R value is 0,068. The geometry around the phosphorus is trigonal bipyramidal with two five-membered rings in the apical-equatorial planes. The three P-O bond lengths are 1,615(5) (equatorial), 1,670(4) and, 1,808(4) Å (apical).     

The crystal and molecular structure of an asymmetric diacetylene monomer, 6-(4-dimethylaminobenzoyloxy)-2,4-hexadiynyl 3,5-dinitrobenzoate

The crystal and molecular structure of an asymmetric diacetylene derivative, 6-(4-dimethylaminobenzoyloxy)-2,4-hexadiynyl 3,5-dinitrobenzoate ( 1 ), was determined from x-ray diffraction data. The crystals are monoclinic, P2₁/c with Z = 4 in a unit cell having dimensions, a = 11,116 (1) Å, b = 13,429 (2) Å, c = 14,672 (3) Å, β = 106,84 (6)°. The structure was solved by direct methods and refined by least-squares techniques to an R_F of 6,2% for 1 991 independent reflections. The diacetylene backbone chains are almost perfectly parallel to the ac-plane; however, they are displaced from each other in the [010] direction. The solid-state polymerization mechanism is discussed with respect to the geometric disposition of the diacetylene chains, which in this crystal are too far apart to permit polymerization by means of 1,4-addition, consistent with the Baughman mechanistic model.     

Solid state polymerization of zinc methacrylate

Zinc methacrylate has been polymerized in the solid state by the post-irradiation technique at 89.5°C. The polymer produced was less isotactic than that obtained from barium methacrylate dihydrate when polymerized under similar conditions. The tacticity of the poly(zinc methacrylate) differed markedly from the polymer produced in the liquid phase from methyl methacrylate or methacrylic acid. X-ray studies of the zinc methacrylate showed the monomer to have an orthorhombic unit cell with lattice constants of a = 17.94Å, b = 9.16 Å, and c = 13.2 Å. There are 8 molecules per unit cell and the symmetry can be classified as either Pnam or Pna2. The anhydrous monomer shows pronounced thermal polymerization at 89.5°C and the radiation-induced reaction shows no measurable intensity dependency over a 6 fold change in dose rate.     

The crystal structure of polylauryllactam (nylon 12)

The crystal structure of nylon 12 was determined from the X-ray diffraction patterns of uniaxially oriented specimens. The unit cell is monoclinic (pseudo-hexagonal) with the following dimensions: a = 4,79 Å, b = 31,9 Å (fiber axis), c = 9,58 Å, β = 120°. There are four monomeric units in the unit cell and the space group is P2₁/c. The structure presents a distortion of the amide group from the planar chain conformation and it is rather similar to γ-nylon 6. The hydrogen bond length is about 2,80 Å and the molecular packing is characterized by alternate, “up and down”, highly disordered sheets of parallel chains, linked by hydrogen bonds. The agreement between observed and calculated intensities has been improved by introducing a statistical disorder.     

Structural chemistry of polymerizable monomers, 4. Crystal and molecular structure of N-methyldimethacrylamide and its effects on the initial stage of solid-state cyclopolymerization

The structure of N-methyldimethacrylamide was solved by direct methods and refined to a discrepancy index (reliability factor) R = 0,055 and weighted discrepancy index R_w = 0,068. C₉H₁₃NO₂, relative molecular mass M_r = 167,21, monoclinic, C 2/c, a = 11,882 (1), b = 8,130 (1), c = 10,079 (1) Å, β = 94,21 (1)°, V = 971,0 (1) ų, D_cal (Z = 4) = 1,143, D _obs = 1,16 Mg · m^?3, μ(MOK_a) = 0,087 mm^?1, mp 364 K, colourless needle crystal by sublimation. The molecule has a crystallographic C₂ symmetry. The shortest spacing between vinyl carbon atoms in the molecule is 2,908 (2) Å (C(3)…C(3′)). Planes of two intramolecular vinyl groups assume a dihedral angle of 40,6 (4)°. It seems that the location of the vinyl carbon atoms allows an intramolecular closure in the initiation process, that is, tail-to-tail cyclization as observed. The subsequent solid-state reaction probably proceeds through dimerization predominantly along a plane near the (1 01) plane in the lattice.     

Unit cell dimensions of poly(ethylene terephthalate)

The density of crystals of poly(ethylene terephthalate), (PETP), Q_c is checked by X-ray diffraction assuming a triclinic unit cell and the indices of reflections as found by Bunn. The following unit cell dimensions are found: a = 4,48Å, b = 5,85Å, c = 10,75 Å, α = 99,5°, β = 118,4°, and γ = 111,2°. This gives the density Q_c as 1,515g/cm³ which is about 4% higher than that reported by Bunn. Negligible differences in spacings for samples annealed at different temperatures (120°C–260°C) have been found. Only for an annealing temperature of 100°C the higher d-values lead to Q_c = 1,484g/cm³. For undrawn PETP films annealed at 250°C the same value of Q_c as for drawn PETP was obtained on the basis of Guinier X-ray patterns. No systematic variation of crystal plane spacings was found for drawn PETP fibers annealed at 220°C and containing mole fractions of 1,7 to 4,2% diethylene glycol, (2,2′-oxydiethanol), as comonomer.     

Structural studies on 1,4-cis-poly(2-methyl-1,3-pentadiene) synthesized with Nd catalysts

(E)-2-Methyl-1,3-pentadiene was polymerized with the AlEt₂Cl-Nd(OCOC₇H₁₅)₃-Al(iBu)₃ system to a polymer consisting of 98–99% 1,4-cis-structure. The crude polymer was fractionated by successive extractions with boiling diethyl ether, heptane and toluene. Examination of the soluble fractions and of the residue to toluene extraction by NMR, X-ray and DSC techniques indicated that the crude polymer consists of macromolecules differing in stereoregularity. Evidence is reported that the crystalline residue after the toluene extraction has a 1,4-cis-isotactic structure. The existence of two different crystalline phases is shown and the respective cell parameters have been determined. α-Phase: a = 10,74, b = 13,04, c = 7,87 Å (?120°C), space group Pbca, Z = 8, D_c = 1,00 g · cm^?3. β-phase: a = 9,30, b = 7,73, c = 7,90 Å (25°C), space group P2₁2₁2₁Z = 4, D_c = 0,96 g · cm^?3.     

The addition halogenation of poly(1-alkenylene)s, 5 X-ray crystal structures of (RS)-1,2,5,6-tetrachlorohexane and (RRSS)-2,3,6,7-tetrachlorooctane

The high melting and most easily crystallizable products of the isomer mixtures obtained by addition chlorination of 1,5-hexadiene and cis,cis-2,6-octadiene were found, by X-ray analysis, to be the meso stereoisomers (RS)-1,2,5,6-tetrachlorohexane (TCH) and (RRSS)-2,3,6,7-tetrachlorooctane (threo-disyndiotactic structure) (TCO) respectively. The carbon atoms in both structures are in a nearly planar zigzag, while the side chlorine atoms are in a gauche position in respect of the carbon atoms. These molecular structures are compared with those of the crystalline chain segments obtained by addition chlorination of cis and trans poly(1-alkenylenes). The crystals of TCH are monoclinic, space group P2₁/n, with Z=2 in a unit cell having dimensions: a=9,02±0,03, b=10,09±0,03, c=5,23±0,02 Å β=100°12′±20′. The crystals of TCO are monoclinic, space group P2₁/n, with Z=2, in a unit cell of dimensions: a=10,97±0,03, b=8,66±0,02, c=6,27±0,02 Å, β=101°55′±20′. The X-ray analysis has been performed with a Stoë-automated Weissenberg camera. The structures have been refined by least-square techniques to R=0,06 for 1076 reflections in the case of TCH and R=0,078 for 973 reflections in the case of TCO.     

Single crystal structure of a polymerization active Nd-Al bimetallic complex

A polynuclear Nd-Al bimetallic complex in single crystalline form, which is active for diene polymerization, was isolated and its detailed structure was determined by X-ray diffraction technique. The results indicate that the crystal is triclinic, space group P1 ; the lattice parameters are: a = 15,195(6), b = 15,263 (5), c = 13,749 (4) Å; α = 90,01 (2), β = 95,12 (3), γ = 82,65 (3)°; V = 3149,5 ų; Z = 1. The coordination number of the Nd atom is seven and the configuration is monocap-prism. Nd atoms can be divided into three groups according to their coordination environment.     

Crystal structure of orthorhombic polyselenomethylene

A new crystalline form of polyselenomethylene is described with an orthorhombic unit cell space group P2₁2₁2₁ and lattice constants a = 5.37Å, b = 9.03Å, c = 4.27Å. The chains are helicoidal with the axis of the helix parallel to c. The identity period of 4.27 Å comprises two monomeric units and one turn of the helix.     

Molecular and crystal structure of bis(4-mercaptophenyl) sulfide as a model compound for poly(1,4-phenylene sulfide)

The molecular and crystal structure of bis(4-mercaptophenyl) sulfide ( 3 ) was determined by means of an X-ray diffraction analysis. The crystals are monoclinic, P2₁ /n with four molecules in the unit cell of the dimensions: a = 5,752 (1), b = 25,767 (9), c = 7,954 (2) Å and β = 95,2 (1)°. The structure was solved by direct methods and refined by least-squares techniques up to R = 0,075 for 1 280 independent reflections. The molecules of 3 do not have own symmetry and are arranged in the unit cell in chains along the 2₁ axes. Between sulfur atoms of neighbouring molecules hydrogen bonds are formed. From investigations of 3 and poly(1,4-phenylene sulfide) ( 2 ) at low temperatures (down to 90 K) similarities of changes in the crystal structures of both substances were evidenced.     

Crystal and molecular structure of 1,4-bis(chloroacetyl)-trans-2,5-dimethylpiperazine,a model compound of poly(trans-2,5-dimethyl-1,4-piperazinediylfumaroyl)

The molecular and crystal structure of 1,4-bis(chloroacetyl)-trans-2,5-dimethylpiperazine synthesized by us, was determined from X-ray diffractometer data. The structure was solved by Patterson and Fourier methods and refined by least-squares techniques to R 0,065 for 1081 independent reflections. The crystals are monoclinic, space group P2₁/n, with Z = 2 in a unit cell of dimensions: a = 9,486 (6), b = 9,139 (6), c = 7,036 (5) Å, β = 95,73 (10)°, the numbers in parentheses being the estimated standard deviations refering to the last significant digit. The trans-2,5-dimethylpiperazine ring is in a flattened-chair conformation with the side methyl groups in axial position. The atoms of the amide are nearly coplanar. It seems to be proved that the structure of the trans-2,5-dimethylpiperazine ring in poly(trans-2,5-dimethyl-1,4-piperazinediylfumaroyl) is similar to that found for 1,4-bis(chloroacetyl)-trans-2,5-dimethylpiperazine.     

The crystal structure of polycapryllactam (nylon 8) and of polycapriclactam (nylon 10)

From X-ray diffraction patterns of uniaxially oriented fibers, the structures of Nylon 8 and Nylon 10 were determined. They crystallize in the monoclinic system (pseudohexagonal), space group P2₁/b, with four monomeric units in the unit cell. The crystallographic parameters of Nylon 8 are: a=4,77; b=9,54; c=21,9 Å; γ=120°, and those of Nylon 10: a=4,78; b=9,56; c=26,9 Å; γ=120° (c fiber axis). Both structures show a γ-type molecular packing, characterized by a shortening of the fiber repeat distances and by a twisting of the amide groups. Therefore, pleated sheets of parallel chains joined by hydrogen bonds are formed and the direction of the chains in adjacent sheets is alternately “up and down”. These structures result very similar to those of Nylon 6 and Nylon 12 in γ-form, demonstrating once more that, in this series, by increasing the number of methylene groups, the usual crystal structure becomes the γ-form.     

Crystal structure of the form I of syndiotactic poly(1-butene)

The crystal structure of the form I of syndiotactic poly(1-butene) is presented. According to the present analysis, chains having s(2/1)2 helical conformation are packed in an orthorhombic unit cell with a = 16,81 Å, b = 6,06 Å and c = 7,73 Å. The density is 0,96 g/cm³ with two chains in the cell (8 monomeric units), the space group is C222₁. Disorder, corresponding to the statistical presence of right- and left-handed helices in each site of the lattice, could be present. The space group for the completely disordered structure is Cmcm.