The crystal sructure of lauric acid

Vand, V.; Morley, W. M.; Lomer, T. R.

doi:10.1107/s0365110x51001069

Cited by 96 publications

(35 citation statements)

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“…Apart from pure palmitic acid, all mixtures were exclusively present in the 74-form (nomenclature according to Precht [2]). This modification is in agreement with the C-form of Vand et al [3]. SP0 did not only show the presence of the ~/4-form but also the fl2-modifieation (Bform of Larsson and yon Sydow [4]).…”

Section: Description Of X-ray Diffraction Patternssupporting

confidence: 89%

Crystal structures of binary systems of saturated fatty acids

Frede¹,

Precht²

1976

J Americ Oil Chem Soc

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Data on crystal lattices of t 3 different mixtures of the system palmitic acid:stearic acid (C16/C18) could be obtained by means of X-ray and electron diffraction. The modification occurring in all concentrations was found to be in conformity with the known74-or C-form of the pure components. It is characterized by the fact that, in mixtures with 95-60 mol % stearic acid, the shorter chained palmitic acid molecules may be incorporated in the crystal lattice of pure stearic acid without dimension c of the unit cell being changed. In concentration ranges of 50-20% C18molecules, one form of mixture which proves to be stable is characterized by constancy of nearly all unit cell parameters of various mixture ratios. From SP10 to SP0, the lattice constants of pure palmitic acid are mainly obtained. The occurrence of C18-molecules of up to 10% in the unit cell of palmitic acid results in a flight decrease of the angle fl by 1-2 ° and an enlargement of the distance to neighbored molecules.

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Section: Description Of X-ray Diffraction Patternssupporting

confidence: 89%

Crystal structures of binary systems of saturated fatty acids

Frede¹,

Precht²

1976

J Americ Oil Chem Soc

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“…The H-atom B values ranged from 2.9 to 9.0 ,~2 with a mean of 5.0 ~2. DAC1 and similar to that found for lauric acid (Vand, Morley & Lomer, 1951). The chain length as measured from N(1) to C(12) is 15.155 (5),~,.…”

Section: Commentsupporting

confidence: 54%

n-Dodecylammonium Chloride

Silver¹,

Marsh²,

Frampton³

1995

Acta Crystallogr C

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The redetermination of the structure of C12H28N+.C1 -corroborates and complements the limited data of a prior less accurate study. The structure consists of C12H28N ÷ chains arranged head-to-tail in layers between layers of C1-ions. CommentThe structure of dodecylammonium bromide has been reported previously along with a preliminary (projection) determination of dodecylammonium chloride (Gordon, Stenhagen & Vand, 1953). A more recent study of decylammonium chloride (DACI) and dodecylammonium chloride (DDAC1) (Pinto, Vencato, Gallardo & Mascarenhas, 1987) resulted in the latter complex being solved from only 337 observed reflections using isotropic displacement factors. It was suggested (Pinto et al., 1987) that the finding that the reflection intensities were weak for both compounds was perhaps due to the closeness of a phase transition (Gault, Gallardo & Muller, 1985), which may provoke crystalline disorActa Crystallographica Section C ISSN 0108-2701 ©1995 J. SILVER, P. J. MARSH AND C. S. FRAMPTON 2433 der. Unfortunately, the temperature of the data collection was not reported (Pinto et al., 1987). As part of a programme of work on layer structures, we wished to have a more accurate solution of DDAC1, (I), and we report here the results of that study. (I) "I~he present structure was solved using 1299 observed reflections and 239 variables (reflection to parameter ratio 5.44:1, which is just acceptable). The refinement also included H atoms. The structure of (I) is shown in Fig. 1 and a packing diagram is presented in Fig. 2. The structure is essentially the same in layout as previously reported (Pinto et al., 1987). The bond lengths, however, are more accurate. Refinement of the H atoms led to C--H distances in theorange 0.86-1.10,~ and N--H distances of 0.83-1.05 A. The H-atom B values ranged from 2.9 to 9.0 ,~2 with a mean of 5.0 ~2. DAC1 and similar to that found for lauric acid (Vand, Morley & Lomer, 1951). The chain length as measured from N(1) to C(12) is 15.155 (5),~,.The carbon chains form a layer so that the tail of one stops just short of the next CI-layer and the NHJ-heads of the three neighbouring chains overlap this tail balancing the charge in the C1-layer. Thus, the packing of the carbon chains can be considered as two interdigitated layers (Fig. 2). At 318 K, DDAC1 is found to undergo a phase transition to an interlayer spacing of 30A (Gault et al., 1985). This spacing is about double the chain length and could be explained by the two interdigitated layers in the low-temperature phase moving apart in the high-temperature phase allowing the chains the freedom to rotate. ExperimentalThe title compound was prepared from n-dodecylamine and HCI. Crystals were grown from an ethanol solution.('~ (~ The displacement ellipsoids are drawn at 50% probability levels and H atoms are drawn as small circles of arbitrary radii. Crystalline cohesion is achieved by ionic bonds between the --NH~ cations and the C1-anions, and van der Waals interactions between the carbon chains. There are three close CI(1...

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“…The packing of the hydrocarbon chains is such that there are two acid di~ners per unit cell. The arrangenlent of these carboxyl dimers has also been assu~ned to be the same as in lauric acid (16). The 0-H bond length of the carboxyl group has been taken as 1.04 (17) and hence the interproton distance in the carboxyl dimer as 2.40 A.…”

Section: Discussionmentioning

confidence: 99%

“…The dimensions of the monoclinic unit cell used to calculate the intern~olecular distances in the C-form of stearic acid are from the X-ray diffraction results of Abrahamsson and von Sydow (15). The tilt of the hydrocarbon chains has been assumed to be the same as that of lauric acid, 54'52' to the basal (001) plane containing the carboxyl groups (16). The packing of the hydrocarbon chains is such that there are two acid di~ners per unit cell.…”

Section: Discussionmentioning

confidence: 99%