Spectroscopic studies in the lactam series. I

Shablygin, M. V.; Shigorin, D. N.; Mikhailov, N. V.

doi:10.1007/bf00653887

Cited by 4 publications

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“…Computational calculations are useful to predict positions of the vibrational IR transitions and to help define these ambiguous assignments. For instance, our data reveal that the experimental band at 3260 cm −1 is more likely to correspond to the lactamic N-H stretching, supporting the assignments done by Yang et al and Ferraro et al 32,33 As can be seen in Table III (compare UCB values against free γ -lactam, pyrrole and propionic acid values), 35,[37][38][39] hydrogen bonding in UCB causes a redshift of all the stretching bands of the groups involved in the interaction.…”

Section: Infrared Vibrational Frequencies and Hydrogen Bonding Enesupporting

confidence: 90%

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Computational chemical analysis of unconjugated bilirubin anions and insights into pKa values clarification

Vega-Hissi

Estrada

Lavecchia

et al. 2013

The Journal of Chemical Physics

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The pKa, the negative logarithm of the acid dissociation equilibrium constant, of the carboxylic acid groups of unconjugated bilirubin in water is a discussed issue because there are quite different experimental values reported. Using quantum mechanical calculations we have studied the conformational behavior of unconjugated bilirubin species (in gas phase and in solution modeled implicitly and explicitly) to provide evidence that may clarify pKa values because of its pathophysiological relevance. Our results show that rotation of carboxylate group, which is not restricted, settles it in a suitable place to establish stronger interactions that stabilizes the monoanion and the dianion to be properly solvated, demonstrating that the rationalization used to justify the high pKa values of unconjugated bilirubin is inappropriate. Furthermore, low unconjugated bilirubin (UCB) pKa values were estimated from a linear regression analysis.

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Section: Infrared Vibrational Frequencies and Hydrogen Bonding Enesupporting

confidence: 90%

“…37,40,41 Hydrogen bonding produces a redshift and an intensification of the stretching ν(X-H) vibration. In order to estimate the hydrogen bond strength in UCB, we used the simple Badger-Bauer rule:…”

Section: Infrared Vibrational Frequencies and Hydrogen Bonding Enementioning

confidence: 99%

Computational chemical analysis of unconjugated bilirubin anions and insights into pKa values clarification

Vega-Hissi

Estrada

Lavecchia

et al. 2013

The Journal of Chemical Physics

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“…Somewhat less obvious is the effect of small-angle ring strain and rehybridization within pyrrolidone on its N─H in-plane bending frequency. In trans secondary amides, the N─H in-plane bending is strongly coupled with the C─N stretching, giving rise to the amide II vibrational frequency near 1550 cm −1 (3,48,51). Since lactams having fewer than nine members exist exclusively in the s-cis conformation, it is generally stated that they show no amide II band in the 1500-1600 cm −1 region (4,39,51).…”

Section: Ir Of Pyrrolidones and Caprolactamsmentioning

confidence: 99%

“…In trans secondary amides, the N─H in-plane bending is strongly coupled with the C─N stretching, giving rise to the amide II vibrational frequency near 1550 cm −1 (3,48,51). Since lactams having fewer than nine members exist exclusively in the s-cis conformation, it is generally stated that they show no amide II band in the 1500-1600 cm −1 region (4,39,51). However, in s-cis lactams, coupling of the N─H in-plane bending with the C─N stretching gives rise to an absorption peak analogous to the amide II band but appearing in the 1350-1500 cm −1 region.…”

Section: Ir Of Pyrrolidones and Caprolactamsmentioning

confidence: 99%

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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“…In decyclization of acid amides (lactams) in production of aliphatic polyamides, dissociation of lactam dimers is the first stage of the reaction [2,3]. As the spectral studies showed, the cis-form of the amide group causes the formation of a double associate of chelate form:…”

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confidence: 99%

Role of the intermolecular interaction in polymer fibre chemistry and technology

Shablygin

2006

Fibre Chem

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The existence of a specific intermolecular interaction of a hydrogen bond affects many polymerization processes and the occurrence of reactions in the chains of macromolecules. The features of the hydrogen bond in monomeric and oligomeric compounds are revealed. In production of aromatic polyamides, polyamido acids, polyimides, and the fibres based on them, the role of the hydrogen bond is reduced to the possibility of deliberate regulation of the chain rigidity.The intermolecular interaction (IMI) between molecular groups of monomeric and polymeric compounds active in its formation are very important in polymerization processes and also determines the features of fibre formation, properties of the fibres, and performance parameters of the articles made from them.The dipole-dipole interaction, H-bond, and π-π-electron interaction determine the kinetic and thermodynamic characteristics of polymer formation to a significant degree, including polycondensation, decyclization, and cyclodehydration of polymer systems. In addition, the orientation-crystallization processes that accompany fibre formation are also intentionally regulated by different types of IMI.The specific effect of the H bond occupies a special position among associative systems. It exists in many monomeric compounds, entering into polymerization, and in their reaction with polymer systems.Hydrogen bonding changes the electron-oscillation characteristics of groups active in formation of H bonds. In all cases, the frequency shifts can consist of 100-200 to 300-400 cm -1 , identified by vibrational, IR, and Raman spectroscopy [1]. A similar picture is observed for chemical shifts in nuclear magnetic resonance. The more important the frequency shifts and the greater the half-width of the corresponding bands, the higher the energy of the H-bonds.Let us consider some cases of the effect of the H-bond in the chemistry and technology of fibre-forming polymers. In decyclization of acid amides (lactams) in production of aliphatic polyamides, dissociation of lactam dimers is the first stage of the reaction [2, 3]. As the spectral studies showed, the cis-form of the amide group causes the formation of a double associate of chelate form:If n ≥ 7, the amide group is in the trans-form, the double H-bond passes into the n-dimensional form with a smaller frequency shift of (NH) stretching vibrations perturbed by the H-bond, from 210 to 120 cm -1 , respectively. The half-width of the NH bond absorption bands decreases from 50-60 to 20-25 cm -1 . Polymerization with rupture of the CN-bond ring in lactams takes place with formation of the trans-form of the amide group with reduced H-bond energy. The mechanism of hydrolytic polymerization is based on the reaction of lactam dimers with water. The energy of formation of an H-bond between water and the cis-form of the amide group decreases, which breaks the CN bond in the ring and causes polymerization.Moscow State Textile University.

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Spectroscopic studies in the lactam series. I

Cited by 4 publications

References 4 publications

Computational chemical analysis of unconjugated bilirubin anions and insights into pKa values clarification

Computational chemical analysis of unconjugated bilirubin anions and insights into pKa values clarification

Introduction to Pyrrolidone and Caprolactam Chemistry

Role of the intermolecular interaction in polymer fibre chemistry and technology

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