Medium-ring compounds. XX. Caprolactam hydrochloride

Winkler, F. K.; Dunitz, J. D.

doi:10.1107/s0567740875002452

Cited by 17 publications

(10 citation statements)

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“…From the perspective of resonance theory, O-protonation is preferred since the positive charge can be delocalized (Figure 18). Indeed, the amide oxygen is protonated in the X-ray crystal structure of caprolactam hydrochloride (229). Consistent with resonance theory, protonation results in a shortening of the N-C(O) bond by 0.060 Å and a lengthening of the C─O bond by 0.079 Å, relative to neutral, unprotonated caprolactam (25).…”

Section: Brønsted and Lewis Basicity Of Pyrrolidones And Caprolactamssupporting

confidence: 60%

Introduction to Pyrrolidone and Caprolactam Chemistry

Chenault

2021

Handbook of Pyrrolidone and Caprolactam Based Materials

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Pyrrolidones and caprolactams are important structural components of solvents, surfactants, polymers, natural products, and pharmaceuticals. This chapter provides an introduction to the structure, conformation, physical properties and reactivity of pyrrolidones and caprolactams. It begins with an overview of the nomenclature of lactams since there are several systems of nomenclature in practice, plus common names and various syncretisms. Next, the structures of pyrrolidone and caprolactam are discussed, starting with the X-ray crystal structures of pyrrolidone, N-methylpyrrolidone (NMP) and caprolactam. The conformational flexibility and ring strain of the two ring systems are also covered.Physical properties, such as dipole moments, the enthalpies of formation, vaporization and fusion, boiling points and melting points, are described. An attempt is made to put the properties of pyrrolidones and caprolactams into context with those of other lactams, amides and even lactones and cyclic ketones. Brønsted and Lewis basicity, acidity, hydrogen bonding and solubility are covered.Finally, a brief description of the basic reactivity of pyrrolidones and caprolactams is given. Topics covered are N-, O-, and α-C-alkylation, hydrolysis, reactions with organometallics, reduction, oxidation, and ring-opening polymerization. The intent is to give a concise physical organic perspective on reactivity (and stability) more than an extended treatise on synthetic elaborations. Definition and Nomenclature of LactamsLactams are cyclic amides in which both the carbonyl carbon and nitrogen atom of the amide group are part of a ring. The name, lactam, is a portmanteau of lactone (cyclic ester) and amide.Nomenclature of lactams follows a variety of conventions (Figure 1 and Table 1). The International Union of Pure and Applied Chemistry (IUPAC) recommends naming lactams as heterocyclic pseudoketones (IUPAC method 1) or by substituting lactam for the

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Section: Brønsted and Lewis Basicity Of Pyrrolidones And Caprolactamssupporting

confidence: 60%

Introduction to Pyrrolidone and Caprolactam Chemistry

Chenault

2021

Handbook of Pyrrolidone and Caprolactam Based Materials

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“…It also can play a role of donor or acceptor of a hydrogen bond involving NH or C = O group [4][5][6]. In acidic media the carbonyl group of the cpl can be protonated resulting either in an isolated Hcpl + cation as in the caprolactam hydrochloride [7] or in a dimeric cation H(cpl) 2 + in (H(cpl) 2 ) 3 [Cr(NCS) 6 ] [8].…”

Section: Introductionmentioning

confidence: 99%

Hydrogen bonding induced polymorphism in the scandium(III) complex with ε-caprolactam

Вировец¹,

Cherkasova

Peresypkina³

et al. 2015

Zeitschrift Für Kristallographie - Crystalline Materials

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Two polymorphs of [Sc(cpl) 6 ][Cr(NCS) 6 ] (cpl = ε-C 6 H 11 NO), trigonal and monoclinic, form purple elongated narrow plates and brownish-purple prisms and are formed concomitantly irrespectively of the crystallization conditions. In the trigonal polymorph both cation and anion possess C 3i site symmetry while in the monoclinic form cation and anion lie on inversion centre and 2-fold axis respectively. The nature of the polymorphism traces back to a redistribution of inter-and intramolecular hydrogen bonds that causes different conformation of the complex cations, different hydrogen bonding and different molecular packings. The [Sc(cpl) 6 ] 3+ cations in the structure of the trigonal polymorph form intermolecular N(H)…S, and in the monoclinic form both N(H)…S inter-and N(H)… O intramolecular hydrogen bonds with NCS groups of [Cr(NCS) 6 ] 3− and cpl ligands. This aggregation leads to chains, where the cations and the anions alternate, in the trigonal modification and to layers, in which each ion is surrounded by four counterions, in the monoclinic form. Both polymorphs possess thermochromic properties, and a reversible color change from light purple to dark green takes place at 470-475 K.

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“…Replacement of the C=C double bond by the protonated amide group has apparently almost no effect on the ring conformation. Analysis of the experimental thermal-motion tensors in terms of rigid-body translational and librational motion (Schomaker & Trueblood, 1968) The dimensions of the protonated cis-amide group, as determined from this analysis, are somewhat more accurate than those from the caprolactam hydrochloride analysis (Winkler & Dunitz, 1975). The bond angles (apart from the poorly determined ones involving the H atoms) agree well, but there are appreciable apparent differences between corresponding bond lengths.…”

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confidence: 80%

“…The crystals, prepared in the same way H(1) C(3) 172 (3) as those of caprolactam hydrochloride (Winkler & I-1(2) c(3) 155 (3) H(1) C(4) -18 (3) Dunitz, 1975), are much less hygroscopic but they H(2) C(4) 63 (3) were also sealed in capillaries since they disintegrate H(1) C(5) 159 (4) slowly in air.…”

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confidence: 99%