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Molecules, Volume 4, Issue 4 (April 1999), Pages 81-121, Articles M92-M94

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Open AccessArticle Benzothiazole Derivatives. 48. Synthesis of 3-Alkoxycarbonylmethyl-6-bromo-2-benzothiazolones and 3-Alkoxycarbonylmethyl-6-nitro-2-benzothiazolones as Potential Plant Growth Regulators
Molecules 1999, 4(4), 81-93; doi:10.3390/40400081
Received: 17 March 1998 / Accepted: 8 March 1999 / Published: 26 March 1999
Cited by 19 | PDF Full-text (76 KB)
Abstract
3-Alkoxycarbonylmethyl-6-bromo- and 3-alkoxycarbonylmethyl-6-nitro-2-benzothiazolones were synthesized by reaction of alkylesters of halogenoacetic acids with 6-bromo-2-benzothiazolones and 6-nitro-2-benzothiazolones respectively. The compounds were tested for plant growth stimulating activity on wheat (Triticum aestivum). The bromo derivatives manifested 25.4 % average stimulating activity in [...] Read more.
3-Alkoxycarbonylmethyl-6-bromo- and 3-alkoxycarbonylmethyl-6-nitro-2-benzothiazolones were synthesized by reaction of alkylesters of halogenoacetic acids with 6-bromo-2-benzothiazolones and 6-nitro-2-benzothiazolones respectively. The compounds were tested for plant growth stimulating activity on wheat (Triticum aestivum). The bromo derivatives manifested 25.4 % average stimulating activity in comparison with the control. The stimulation activity of the nitro derivatives was not significant. Optimal structures of the compounds were obtained by a MMPI method, atomic charges and dipole moments were calculated by a semiempirical AM1 method. On the basis of molecular electrostatic potential it has been found that the biological activity of synthesized compounds depends on charge distribution in the molecules. Full article
Open AccessArticle A Study of Acid-Base Equilibria in Acetonitrile Systems of 2-Halo(Cl,Br,I)-4-nitropicoline(3,5,6) N-oxides
Molecules 1999, 4(4), 94-103; doi:10.3390/40400094
Received: 9 March 1998 / Accepted: 8 March 1999 / Published: 29 March 1999
Cited by 3 | PDF Full-text (30 KB)
Abstract
An attempt has been made to determine potentiometrically (1) acid dissociation constants of cations obtained by protonation of nine trisubstituted pyridine N-oxides, namely 2-halo(Cl, Br and I)-4-nitropicoline N-oxides with the methyl group at positions 3, 5, and 6, as well as (2) [...] Read more.
An attempt has been made to determine potentiometrically (1) acid dissociation constants of cations obtained by protonation of nine trisubstituted pyridine N-oxides, namely 2-halo(Cl, Br and I)-4-nitropicoline N-oxides with the methyl group at positions 3, 5, and 6, as well as (2) the cationic homoconjugation constants of these cationic acids with conjugated N-oxides in acetonitrile. On the basis of the substitution effect, variations of the acid dissociation constants of the trisubstituted pyridine N-oxide cations are discussed. The determined pKa values of the protonated 2-halo-4-nitropicoline N-oxides are compared with the previously determined equilibrium constants of the cationic acids conjugated with the mono- and disubstituted pyridine N-oxides in acetonitrile. Further, based on the pKa values of the protonated 2-halo-4-nitropicoline N-oxides in acetonitrile, supplemented with correlations between pKa’s of the protonated mono- and disubstituted pyridine N-oxides in acetonitrile and water, the pKa's of the acids conjugated with the trisubstituted N-oxides studied in aqueous solutions have been estimated. Moreover, it has been concluded that the cationic homoconjugation constants cannot be determined by potentiometric titration in acetonitrile solutions of the 2-halo-4-nitropicoline N-oxide systems. Full article
Open AccessArticle X-ray Crystallography at 170 K of Racemic 2,2'-Dimethoxy-9,9'-biacridine and 1H NMR Study of 2,2'-Diacetoxy-9,9'-biacridine
Molecules 1999, 4(4), 104-121; doi:10.3390/40400104
Received: 16 March 1998 / Accepted: 5 May 1998 / Published: 16 April 1999
Cited by 3 | PDF Full-text (140 KB)
Abstract
Three derivatives of 9,9'-biacridine, 2,2'-dihydroxy, 2,2'-dimethoxy and 2,2'-diacetoxy have been prepared. The crystal structure of racemic 2,2'-dimethoxy-9,9'-biacridine CHCl3 1:1 complex has been determined and shows an almost perpendicular conformation of both acridine rings. 1H NMR experiments using the diacetoxy derivative [...] Read more.
Three derivatives of 9,9'-biacridine, 2,2'-dihydroxy, 2,2'-dimethoxy and 2,2'-diacetoxy have been prepared. The crystal structure of racemic 2,2'-dimethoxy-9,9'-biacridine CHCl3 1:1 complex has been determined and shows an almost perpendicular conformation of both acridine rings. 1H NMR experiments using the diacetoxy derivative and both Eu(tfc)3 and R-Pirkle's alcohol show the splitting of some signals characteristic of a racemic compound. Full article

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Open AccessShort Note (-)-b-D-18–Glucopiranosyl-9,15-dihydroxy Kaurenoate, a New Diterpene Glycoside from Ageratina vacciniaefolia
Molecules 1999, 4(4), M92; doi:10.3390/M92
Received: 26 October 1998 / Published: 16 April 1999
Cited by 2 | PDF Full-text (133 KB) | Supplementary Files
(This article belongs to the Section Molbank Section of Molecules, 1997-2001)
Open AccessShort Note Plumbagin from Diospyros olen
Molecules 1999, 4(4), M93; doi:10.3390/M93
Received: 3 February 1999 / Published: 16 April 1999
Cited by 7 | PDF Full-text (93 KB) | Supplementary Files
(This article belongs to the Section Molbank Section of Molecules, 1997-2001)
Open AccessShort Note A New Diglycoside of Diterpene from Ageratina vacciniaefolia
Molecules 1999, 4(4), M94; doi:10.3390/M94
Received: 19 March 1999 / Published: 16 April 1999
Cited by 2 | PDF Full-text (110 KB) | Supplementary Files
(This article belongs to the Section Molbank Section of Molecules, 1997-2001)

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