A comparison between different techniques for the isolation of rosemary essential oil

Traditional hydrodistillation (HD), supercritical fluid extraction (SFE), organic solvent extraction (SE), and water microwave assisted hydrodistillation (MAHD) techniques were compared and evaluated for their effectiveness in the isolation of rosemary essential oil. The microwave assisted hydrodistillation technique was optimized in terms of both delivered power and time duration. The extracts/distillates were analyzed by GC and GC-MS. Microwave distillation, which exploits the physical action of microwaves on plants, showed a series of advantages over the other approaches: low cost, use of water in sample pre-treatment step, greatly reduced isolation time, and attainment of high quality essential oil distillate. Moreover, the absence of environmental impact of this innovative technique was also emphasized.     

Ion chromatographic determination of N-nitrosoglyphosate in a glyphosate matrix

The use of high-performance ion chromatography (HPIC) for the determination of N-nitrosoglyphosate [N-nitroso-N-(phosphonomethyl)glycine] is reported. NMR, spectrophotometric and electroanalytical measurements showed that two conformers of N-nitrosoglyphosate in slow equilibrium are always present. Separation of these conformers is achieved by using appropriate chromatographic conditions. The conductimetric detection of N-nitrosoglyphosate and glyphosate and application to the determination of traces of N-nitrosoglyphosate in complex matrices are also reported.     

Stepwise retro 1,3-dipolar cycloaddition induced by electron. Impact on 3,5-diphenyl-1,2,4-oxadiazole

The retro 1,3-dipolar cycloaddition induced by electron impact on 3,5-diphenyl-1,2,4-oxadiazole is interpreted as a two-step process on the basis of the energetics and kinetics of the fragments [C₇H₅NO]⁺., [C₆H₅CN]⁺. and [C₆H₅CO]⁺.     

1,2-fused pyrimidines. V. Synthesis of 1-alkyl or phenyl-2H-dipyrido-[1,2-a:2′,3′-d]pyrimidine-2,5(1H)-diones

The reaction of 2-[(N-acyl, N-alkyl or phenyl)amino]-4H-pyrido[1,2-a]pyrimidin-4-ones 8a-g with the N,N-dimethylformamide/phosphorus oxychloride Vilsmeier reagent 1 (95°, 90 minutes) afforded 1-alkyl or phenyl-2H-dipyrido[1,2-a:2′,3′-d]pyrimidine-2,5(1H)^?diones, 3-alkyl substituted or not, 10a-g . The starting compounds 8 were prepared by treating 2-amino-4H-pyrido[1,2-a]pyrimidin-4-ones N-alkyl substituted 7a,b or N-phenyl substituted 4 with excess anhydrides (130°, 7 hours) when the 2-(alkylamino) derivatives 7 were used in the reaction, compounds 8 were obtained along with very small amounts of 3-acyl-2-(alkylamino)-4H-pyrido[1,2-a]pyrimidin-4-ones 9 .     

On an alternative cauchy equation in two unknown functions. Some classes of solutions

Summary In this paper we consider the alternative Cauchy functional equationg(xy) g(x)g(y) impliesf(xy) = f(x)f(y) wheref, g are functions from a topological group (X, ·) into a group (S,·). First we prove that, ifS is a Hausdorff topological group andX satisfies some weak additional hypotheses, then (f, g) is a continuous solution if and only if eitherf org is a homomorphism. Then we describe a more general class of solutions forX =R ⁿ .Partially supported by M.U.R.S.T. Research funds (40%)Dedicated to the memory of Alexander M. Ostrowski on the occasion of the 100th anniversary of his birth.     

The Chemistry of Coumarin Derivatives. Part 5. Unusual course of the reaction of 4-hydroxycoumarin and aliphatic aldehydes

The reaction of 4-hydroxycoumarin and certain aliphatic aldehydes affords 1:1 or complex 2:2 adducts besides (or in place) of the expected 2:1 bis(coumarin) adducts. Reaction with heptanal, cyclohexanecarbaldehyde, and pivalaldehyde are reported as representative. The structure of the reaction products was established by spectroscopical techniques, including X-ray analysis, and their formation was mechanistically rationalized. Some of the 1:1 adducts are synthetically useful for the preparation of 3-alkyl-4-hydroxycoumarins.     

A quantitative approach to the recycling of alpha-tocopherol by coantioxidants

A systematic investigation is reported on the regeneration of alpha-tocopherol (alpha-TOH) in homogeneous solution by coantioxidants in order to better understand the mechanism and the factors responsible for the effectiveness of this process. The current availability of thermochemical data concerning the reactants involved in the regeneration reactions, as well as a large number of the kinetic constants for the various reactions involved, allowed us to rationalize the experimental observations collected so far. Three limiting cases have been considered. The first case is that of a coantioxidant irreversibly regenerating alpha-TOH, where the effectiveness of the recycling process depends on the magnitude of the rate constant k(r). The second case is that of a coantioxidant reversibly recycling alpha-TOH, where regeneration can only be observed if the bond dissociation enthalpy value of the coantioxidant is lower or at least close to that of the O-H bond of alpha-tocopherol. The third case is that of a catechol derivative (chosen as a model compound for polyphenolic antioxidants), where recycling of alpha-TOH is feasible even though the BDE value is significantly higher than that of vitamin E. In this case, the driving force for the recycling process is the removal of the semiquinone radical from the catechol derivative by the alpha-tocopheroxyl radical, which makes the regeneration of alpha-TOH practically irreversible.     

On an alternative functional equation related to the Cauchy equation

We consider the following problem: Let (G, +) be an abelian group,B a complex Banach space,a, bB,b0,M a positive integer; find all functionsf:G B such that for every (x, y) G ×G the Cauchy differencef(x+y)–f(x)–f(y) belongs to the set {a, a+b, a+2b, ...,a+Mb}. We prove that all solutions of the above problem can be obtained by means of the injective homomorphisms fromG/H intoR/Z, whereH is a suitable proper subgroup ofG.     

Mild metal-free syn-stereoselective ring opening of activated epoxides and aziridines with aryl borates

A conceptually new, simple and practical method for the syn-nucleophilic displacement of aryl and vinyl epoxides and aryl aziridines with (substituted) phenols, using aryl borates as activating nucleophiles under neutral conditions, is reported.     

Crystal,molecular and electronic structure of 1,1-diaryl-2-halogenoethylenes

On the basis of semiempirical calculations, the conformation of the isolated molecule of 2-bromo-1,1-diphenylprop-1-ene corresponding to the minimum of total energy was determined. Assuming some information on the localization of the molecules in the crystal, also the conformation in a theoretical crystal was studied. The results have been compared with the crystal structure of 2-bromo-1,1-diphenylprop-1-ene, as obtained by X-ray diffraction. From the comparison a slight displacement of the C2 atom was suggested.

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Zusammenfassung Die dem Minimum der Gesamtenergie entsprechende Konformation des isolierten Moleküls von 2-Brom-1,1-diphenylprop-1-en wurde durch halb-empirische Methoden bestimmt. Gewisse Ergebnisse über die Anordnung der Moleküle im Kristall machten es möglich, die Konformation in einem theoretischen Kristall zu untersuchen. Nach Vergleich der Resultate mit der durch Röntgen-Analyse bestimmten Kristallstruktur des 2-Brom-1,1-diphenylprop-1-en wurde eine kleine Verschiebung des C2-Atoms vorgeschlagen.

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Résumé Par le moyen de calculs semiempiriques on a déterminé la conformation de la molécule isolée de 2-bromo-1, 1-diphénilprop-1-ène, correspondant au minimum d'énergie totale. On a aussi étudié la conformation dans le cristal théorique en se basant sur des informations concernant la localisation des molécules dans le cristal. On a comparé ces résultats avec ceux que nous avons obtenus par la détermination de la structure cristalline du 2-bromo-1, 1-diphénilprop-1-ène avec la diffraction des rayons X: cette comparaison nous a porté à déplacer un petit peu l'atome C 2.

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This work was supported by a grant from the Italian Consiglio Nazionale delle Ricerche.