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Molecules, Volume 6, Issue 4 (April 2001), Pages 287-423

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Research

Open AccessArticle Photooxidation of n-Hexanal in Air
Molecules 2001, 6(4), 287-299; doi:10.3390/60400287
Received: 21 November 2000 / Revised: 11 December 2000 / Accepted: 12 December 2000 / Published: 31 March 2001
Cited by 13 | PDF Full-text (230 KB) | HTML Full-text | XML Full-text
Abstract
Dilute mixtures of hexanal in synthetic air (up to 100 ppm) were photolyzed with fluorescent UV lamps (275-380 nm) in air at 298 K. The main photooxidation products, identified and quantitatively analyzed by FTIR spectroscopy, were butene, CO, vinylalcohol and ethanal. The [...] Read more.
Dilute mixtures of hexanal in synthetic air (up to 100 ppm) were photolyzed with fluorescent UV lamps (275-380 nm) in air at 298 K. The main photooxidation products, identified and quantitatively analyzed by FTIR spectroscopy, were butene, CO, vinylalcohol and ethanal. The photolysis rates and the absolute quantum yield Φ were found to be slightly dependent on the total pressure. At 100 Torr, Φ100 = 0.43 ± 0.02, whereas at 700 Torr the total quantum yield was Φ700 = 0.38 ± 0.02. These results may be explained by the collisional deactivations of photoexcited molecules. Two decomposition channels were identified: the radical channel C5H11CHO → C5H11 + HCO, and the molecular channel C5H11CHO → C4H8 + CH2=CHOH, having the relative yields of 27 and 73 % at 700 Torr. The product CH2=CHOH tautomerizes to ethanal. Full article
Open AccessArticle Synthesis and Electrophilic Substitution of Pyrido[2,3,4-kl]-acridines
Molecules 2001, 6(4), 300-322; doi:10.3390/60400300
Received: 28 February 2001 / Revised: 7 March 2001 / Accepted: 7 March 2001 / Published: 31 March 2001
Cited by 13 | PDF Full-text (173 KB) | HTML Full-text | XML Full-text
Abstract
Several new pyrido[2,3,4-kl]acridines were synthesized by reacting naphthoquinone, juglone or cyclohexan-1,3-dione with β,β’-diaminoketones in a biomimetic reaction. The structure of all new compounds was elucidated by NMR and MS spectroscopy. Electrophilic substitution, mainly nitration, of the various compounds was undertaken and the [...] Read more.
Several new pyrido[2,3,4-kl]acridines were synthesized by reacting naphthoquinone, juglone or cyclohexan-1,3-dione with β,β’-diaminoketones in a biomimetic reaction. The structure of all new compounds was elucidated by NMR and MS spectroscopy. Electrophilic substitution, mainly nitration, of the various compounds was undertaken and the substitution positions determined. A series of derivatives was prepared and their cytotoxicity towards P-388 mouse lymphoma cells analysed. The most cytotoxic derivatives were found to have IC50’s of 0.05 and 0.1 ug/ml. Full article
Open AccessArticle Synthesis of Substituted 2-Benzoylaminothiobenzamides and Their Ring Closure to Substituted 2-Phenylquinazoline-4-thiones
Molecules 2001, 6(4), 323-337; doi:10.3390/60400323
Received: 4 December 2000 / Revised: 6 March 2001 / Accepted: 23 March 2001 / Published: 31 March 2001
Cited by 15 | PDF Full-text (155 KB) | HTML Full-text | XML Full-text
Abstract
Acylation of 2-aminothiobenzamide or 2-methylaminothiobenzamide with substituted benzoyl chlorides has been used to synthesise the corresponding 2-benzoylaminothiobenzamides whose subsequent sodium methoxide-catalysed ring closure gives the corresponding quinazoline-4-thiones. These compounds were characterised by means of their 1H- and 13C-NMR spectra. The [...] Read more.
Acylation of 2-aminothiobenzamide or 2-methylaminothiobenzamide with substituted benzoyl chlorides has been used to synthesise the corresponding 2-benzoylaminothiobenzamides whose subsequent sodium methoxide-catalysed ring closure gives the corresponding quinazoline-4-thiones. These compounds were characterised by means of their 1H- and 13C-NMR spectra. The preferred tautomeric form of selected compounds has been discussed on the basis of their 13C-NMR, IR and Raman spectra. It has been found that in the given medium 1-methyl-quinazoline-4-thiones undergo a replacement of the sulphur substituent by oxygen giving 1-methyl-quinazoline-4-ones. In strong acid media, 2-benzoylaminothiobenzamide is cyclised through its sulphur atom to give 2-phenylbenzo[d-1,3]thiazin-4-one. Full article
Open AccessArticle Malonates in Cyclocondensation Reactions
Molecules 2001, 6(4), 338-352; doi:10.3390/60400338
Received: 21 December 2000 / Revised: 7 March 2001 / Accepted: 8 March 2001 / Published: 31 March 2001
Cited by 27 | PDF Full-text (82 KB) | HTML Full-text | XML Full-text
Abstract
The use of malonates such as diethyl malonates 9, (chlorocarbonyl)ketenes 15 and bis(2,4,6-trichlorophenyl) malonates 18 as reagents for cyclocondensation with 1,3-dinucleophiles to give six-membered heterocycles is described. Further attempts to use malonates such as bis(trimethylsilyl) malonates 19 and bis(carbamimidoyl) malonates 29 as [...] Read more.
The use of malonates such as diethyl malonates 9, (chlorocarbonyl)ketenes 15 and bis(2,4,6-trichlorophenyl) malonates 18 as reagents for cyclocondensation with 1,3-dinucleophiles to give six-membered heterocycles is described. Further attempts to use malonates such as bis(trimethylsilyl) malonates 19 and bis(carbamimidoyl) malonates 29 as new cyclocondensation agents are described . Full article
Open AccessArticle π-Bond Screening in Benzonorbornadienes: The Role of 7-Substituents in Governing the Facial Selectivity for the Diels-Alder Reaction of Benzonorbornadienes with 3,6-Di(2-pyridyl)-s-Tetrazine
Molecules 2001, 6(4), 353-369; doi:10.3390/60400353
Received: 3 November 2000 / Accepted: 6 November 2000 / Published: 31 March 2001
Cited by 5 | PDF Full-text (560 KB) | HTML Full-text | XML Full-text
Abstract
Benzonorbornadiene 21, 7-spirocyclopropylbenzonorbornadiene 23, 7,7-dimethylbenzonorbornadiene 25, and 7-spirocyclopentylbenzonorbornadiene 27 have been reacted with 3,6-di(2-pyridyl)-s-tetrazine (rate: 21>23>25=27) to form symmetrical 4,5-dihydropyridazines which are stable towards fragmentation but rearrange with varying facility to their 1,4 isomers. The facial selectivity of attack on the π-bond [...] Read more.
Benzonorbornadiene 21, 7-spirocyclopropylbenzonorbornadiene 23, 7,7-dimethylbenzonorbornadiene 25, and 7-spirocyclopentylbenzonorbornadiene 27 have been reacted with 3,6-di(2-pyridyl)-s-tetrazine (rate: 21>23>25=27) to form symmetrical 4,5-dihydropyridazines which are stable towards fragmentation but rearrange with varying facility to their 1,4 isomers. The facial selectivity of attack on the π-bond changes from exo-attack for 21 and 23 to endo-attack for 25 and 27. The 7-spirocyclopropyl benzonorbornadiene 23 typically forms a mixture of dihydropyridazines with exo-stereochemistry, which undergo further stereochemical isomerisation to an exo-fused product upon acetylation (acetyl chloride in hot pyridine). Oxidation with DDQ of the dihydropyridazines individually or as mixtures gives the corresponding fused 3,6-di(2-pyridyl)pyridazines. Full article
Open AccessArticle Predicting Vapour Pressures of Organic Compounds from Their Chemical Structure for Classification According to the VOCDirective and Risk Assessment in General
Molecules 2001, 6(4), 370-389; doi:10.3390/60400370
Received: 8 August 2000 / Revised: 22 February 2001 / Accepted: 14 March 2001 / Published: 31 March 2001
Cited by 6 | PDF Full-text (107 KB) | HTML Full-text | XML Full-text
Abstract
The use of organic compounds in the European Union will in the future be regulated in accordance with the Council Directive 1999/13/EC of 11 March 1999 [1]. In this directive, any organic compound is considered to be a volatile organic compound (VOC) [...] Read more.
The use of organic compounds in the European Union will in the future be regulated in accordance with the Council Directive 1999/13/EC of 11 March 1999 [1]. In this directive, any organic compound is considered to be a volatile organic compound (VOC) if it has a vapour pressure of 10 Pa or more at 20oC, or has a corresponding volatility under the particular condition of use. Introduction of such a limit will sometimes create problems, because vapour pressures cannot be determined with an infinite accuracy. Published data on vapour pressures for a true VOC will sometimes be found to be below 10 Pa and vice versa. When the same limit was introduced in the USA, a considerable amount of time and money were spent in vain on comparing incommensurable data [2]. In this paper, a model is presented for prediction of the vapour pressures of VOCs at 20oC from their chemical (UNIFAC) structure. The model is implemented in a computer program, named P_PREDICT, which has larger prediction power close to 10 Pa at 20oC than the other models tested. The main advantage of the model, however, is that no experimental data, which will introduce uncertainty in the predictions, is needed. Classification using P_PREDICT, which only predicts one value for a given UNIFAC structure, is proposed. Organic compounds, which can be described by the UNIFAC groups in the present version of P_PREDICT, therefore, can be classified unambiguously as either VOCs or non-VOCs. Most people, including the present authors, feel uneasy about prioritising precision above accuracy. Modelling vapour pressures, however, could save a lot of money and the errors introduced are not large enough to have any substantial adverse effects for neither human beings nor the environment. A method for calculating vapour pressures at other temperatures than 20oC is tested with a dubious result. This method is used for EU risk assessment of new and existing chemicals. Full article
Open AccessArticle Synthesis of the New Type of Water-Soluble Ligand N,N-Bis-(diphenylphosphinomethyl)-2-aminoethylphosphonic Acid (Ph2PCH2)2NCH2CH2PO3H2 and Its Sodium Salt
Molecules 2001, 6(4), 390-395; doi:10.3390/60400390
Received: 4 July 2000 / Revised: 25 September 2000 / Accepted: 26 September 2000 / Published: 31 March 2001
Cited by 2 | PDF Full-text (115 KB) | HTML Full-text | XML Full-text
Abstract
The novel water-soluble ligand, N,N-bis(diphenylphosphinomethyl)-2-aminoethylphosphonic acid, (Ph2PCH2)2NCH2CH2PO3H2, had been synthesized in quantitative yield by reaction of 2-aminoethylphosphonic acid with bis(hydroxymethyl)-diphenylphosphonium chloride in water. Its mono- and disodium salts, [...] Read more.
The novel water-soluble ligand, N,N-bis(diphenylphosphinomethyl)-2-aminoethylphosphonic acid, (Ph2PCH2)2NCH2CH2PO3H2, had been synthesized in quantitative yield by reaction of 2-aminoethylphosphonic acid with bis(hydroxymethyl)-diphenylphosphonium chloride in water. Its mono- and disodium salts, which can be used as water-soluble ligands for transition metal complex catalysts, were also easily prepared under mild conditions. Full article
Open AccessArticle Synthesis of Some Potentially Bioactive Compounds From Visnaginone
Molecules 2001, 6(4), 396-405; doi:10.3390/60400396
Received: 7 November 2000 / Revised: 19 February 2001 / Accepted: 2 March 2001 / Published: 31 March 2001
Cited by 6 | PDF Full-text (48 KB) | HTML Full-text | XML Full-text
Abstract
The reaction of 5-acetyl-6-hydroxy-4-methoxybenzo[b]furan (visnaginone Ia) with 2-diethylaminoethylchloride led to the formation of 5-acetyl-6-diethylamino-ethoxy-4-methoxybenzo[b]furan (II), whereas condensation of compound II with some aromatic aldehydes afforded the corresponding chalcones IIIa-c. Methylation of visnaginone (Ia) gave 5-acetyl-4,6-dimethoxybenzo[b]furan (Ib), which in turn reacted with some [...] Read more.
The reaction of 5-acetyl-6-hydroxy-4-methoxybenzo[b]furan (visnaginone Ia) with 2-diethylaminoethylchloride led to the formation of 5-acetyl-6-diethylamino-ethoxy-4-methoxybenzo[b]furan (II), whereas condensation of compound II with some aromatic aldehydes afforded the corresponding chalcones IIIa-c. Methylation of visnaginone (Ia) gave 5-acetyl-4,6-dimethoxybenzo[b]furan (Ib), which in turn reacted with some aromatic aldehydes to give the corresponding chalcones IIId,e. The reaction of chalcones IIId,e with hydrazine hydrate in alcohol gave the pyrazoline derivatives IVa,b, whereas when the same reaction was carried out in acetic acid it afforded the N-acetylpyrazoline derivatives Va,b. Similarly, the reaction of IIId,e with phenyl hydrazine in acetic acid led to the formation of phenylpyrazoline derivatives VIa,b, whereas condensation of chalcones IIId,e with hydroxyl amine hydrochloride gave the isoxazoline derivatives VIIa,b. The reaction of compound II with phenylhydrazine and 2,4,6-trichlorophenylhydrazine afforded the corresponding phenyl hydrazone derivatives VIIIa,b. Mannich bases IXa,b were synthesized by the reaction of visnaginone (Ia) with piperidine and benzylamine in the presence of formaline. Full article
Open AccessArticle Bis-Porphyrin Racks with Space-Separated Co-Planar Porphyrin Rings
Molecules 2001, 6(4), 406-416; doi:10.3390/60400406
Received: 7 December 2000 / Revised: 19 March 2001 / Accepted: 21 March 2001 / Published: 31 March 2001
Cited by 6 | PDF Full-text (416 KB) | HTML Full-text | XML Full-text
Abstract A porphyrin appended norbornenyl building block 8 has been isolated and coupled, using a 1,3-dipolar ACE reaction, to yield bis-porphyrin compounds in which the porphyrin moietes are angled upward relative to the norbornane backbone. Full article
Open AccessArticle Synthesis and Characterization of Two New p-tert-Butylcalix[4]-arene Schiff Bases
Molecules 2001, 6(4), 417-423; doi:10.3390/60400417
Received: 12 June 2000 / Revised: 23 January 2001 / Accepted: 24 January 2001 / Published: 31 March 2001
Cited by 4 | PDF Full-text (498 KB) | HTML Full-text | XML Full-text
Abstract
Synthesis and characterization of two new Schiff bases of p-tertbuthylcalix[4]arene (H2L1 and HL2) is described. The synthesis of H2L1 and HL2 has been achieved by the condensation of salicylaldehyde with the amine group [...] Read more.
Synthesis and characterization of two new Schiff bases of p-tertbuthylcalix[4]arene (H2L1 and HL2) is described. The synthesis of H2L1 and HL2 has been achieved by the condensation of salicylaldehyde with the amine group of upper rim monoamine p-tert-butylcalix[4]arene in ethanol. These compounds have been characterized on the basis of elemental analysis and spectral data. Solvatochromicity and fluorescence properties were observed and measured for H2L1 and HL2. Solvatochromicity of these ligands indicates their potential for NLO applications. Full article

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