1989
DOI: 10.1107/s0108270189002064
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Structures of some N-acetylamides of amino acids

Abstract: Abstract. N-Acetylglycinamide (NAGA), C4H8N202, Mr = 116.12, monoclinic, P2Jn, a=5.341 (1), b = 8-041 (2), c= 13.638 (2) A, /3= 93.24 (2) °, V= 584. A(Cu Ka) = 1"54178 A, /x = 0"63 mm-1, F(000) = 376, room temperature, final R = 0.047 for 694 observed reflexions. In the three crystals the molecular packing is ruled by the intermolecular hydrogen bonds which involve all the polar groups. However, in L-NALA the necessity to accommodate increasingly bulky alkyl side chains does not allow the maximum number of po… Show more

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Cited by 17 publications
(22 citation statements)
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“…This behaviour can be ascribed to less effective crystal packing of L-NAAA by comparison with the other amides, which also possess six shared hydrogen bonds in each molecule, but are organized in more compact networks. (28,29) For the cyclopeptides, the fusion temperatures of c-GA and c-AA (and that of decomposition before melting of c-GG) are close to each other and considerably higher than the value found for c-SARSAR. The same pattern was observed for the enthalpies and entropies of fusion.…”
Section: Resultsmentioning
confidence: 54%
“…This behaviour can be ascribed to less effective crystal packing of L-NAAA by comparison with the other amides, which also possess six shared hydrogen bonds in each molecule, but are organized in more compact networks. (28,29) For the cyclopeptides, the fusion temperatures of c-GA and c-AA (and that of decomposition before melting of c-GG) are close to each other and considerably higher than the value found for c-SARSAR. The same pattern was observed for the enthalpies and entropies of fusion.…”
Section: Resultsmentioning
confidence: 54%
“…The first set of data can be rationalised by noting that the NALA molecules share in the crystal only four hydrogen bonds (so that for each molecule there is an energy contribution from two hydrogen bond bridges, see Table 1) whereas for NAGA and NAAA six hydrogen bonds are shared by each molecule in the respective crystals. In the NALA crystals the energy contribution from the third potential hydrogen bond is annulled because of the necessity of accommodating the bulky side chains [4]. Also the density of solid NAGA is about 10% higher than that of L-NAAA and 18% higher than that of L-NALA (1.32, 1.20, 1.12 g cm -3 respectively) and shorter distances for intermolecular contacts, so higher cohesive forces necessarily result.…”
Section: Resultsmentioning
confidence: 98%
“…However, thermodynamic and structural properties of the solid phases of these compounds are interesting per se and, given the lack of information on this class of compounds, we recently have determined a series of crystal structures [4][5][6][7][8][9], and sublimation enthalpies and entropies [5,10,11]. The structures of a few similar compounds have been reported [12][13][14].…”
Section: Introductionmentioning
confidence: 98%
“…The L-NAAA, L-NAVA, and L-NAIA molecules, instead, to better assemble themselves in the crystals, form alternate layers containing either group connected by networks of hydrogen bonds, or hydrophobic groups, so that the crystals are characterized by cleavage planes. (10,25,26) In the L-NALA crystals, the molecules form wrinkled polar sheets making concavities in the shape similar to a half-egg box, in which the twisted leucine side chains settle. (25) Moreover, in this case, only four hydrogen bonds, instead of six, are shared by each molecule.…”
Section: Resultsmentioning
confidence: 98%
“…(10,25,26) In the L-NALA crystals, the molecules form wrinkled polar sheets making concavities in the shape similar to a half-egg box, in which the twisted leucine side chains settle. (25) Moreover, in this case, only four hydrogen bonds, instead of six, are shared by each molecule.…”
Section: Resultsmentioning
confidence: 98%