6,097 research outputs found
PERCHLORATES AS POWERFUL CATALYSTS IN MANY IMPORTANT ORGANIC TRANSFORMATIONS
No full textFor long times, metallic perchlorates have been considered dangerous compounds[1] in that they function as explosives and as incontrollable oxidizers.
Therefore, the fear of the great hazard connected with their manufacture and uses had prevented an extensive use both in research laboratories and in industrial processes.[2]
However, recently it has been cleared that this bad reputation is due to the mistaken association of metallic perchlorates with the oxidizing potential of perchloric acid and the pyrotechnic performances of NH4ClO4.
In this conference, we report that Magnesium and Zinc perchlorates can be used as powerful Lewis acids in several organic transformations which are commonly employed both in laboratory and industrial processes.
As depicted in the Scheme, perchlorates are able to promote a series of reactions such as:
a) Acylation of alcohols[3,4]
b) Fisher esterification[5]
c) Synthesis of b–enamino esters[6]
d) Protection of the amino group as N-Boc derivative[7]
Moreover, they can act as specific catalysts for the development of a new organic transformations. In fact, the treatment of an alcohol or a phenol with Boc2O in the presence of Mg(ClO4)2 leads to the unexpected formation of the corresponding t-butyl ethers.[8] This represents the first general method to synthesize aromatic t-butyl ethers.
In an analogous manner, the treatment of phenols with diethyl dicarbonate results in a very efficient method to produce difficulty available aryl ethyl carbonates.
Several of the above mentioned transformations can be carried out in the absence of the solvent, and often the catalyst can be easily recovered and reused without an appreciable loss of activity.
Acknowledgement
Work carried out in the framework of the National Project “Stereoselezione in Sintesi Organica. Metodologie e Applicazioni” supported by MIUR, Rome, by the University of Bologna, in the framework of “Progetto di Finanziamento Pluriennale, Ateneo di Bologna”, and by National project FIRB “Progettazione, preparazione e valutazione biologica e farmacologica di nuove molecole organiche quali potenziali farmaci”
References
[1] Schumacher, J. C. Perchlorates-Their Properties, Manufacture and Uses, ACS Monograph Series, Reinhold: New York, 1960.Author. Title[J]. Name of the journal, Year, Volume(Issue): initial page and ending page (Optional).
[2] Long, J. Chemical Health & Safety, 2002, 9, 12.
[3] Bartoli, G.; Bosco, M.; Dalpozzo, R.; Marcantoni, E.; Massaccesi, M.; Rinaldi, S.; Sambri, L. Synlett, 2003, 39.
[4] Bartoli, G.; Bosco, M.; Dalpozzo, R.; Marcantoni, E.; Massaccesi, M.; Sambri, L. Eur. J. Org. Chem. 2003, 4611.
[5] a) Gooβen, L.; Döhring, A. Adv. Synth. Catal. 2003, 345, 943; b) Bartoli, G.; Boeglin, J.; Bosco, M.; Locatelli, M.; Massaccesi, M.; Melchiorre, P.; Sambri, L. Adv. Synth. Catal. 2005, 347, 33.
[6] Bartoli, G.; Bosco, M.; Locatelli, M.; Marcantoni, E.; Melchiorre, P.; Sambri, L. Synlett 2004, 239.
[7] Bartoli, G.; Bosco, M.; Locatelli, M.; Marcantoni, E.; Massaccesi, M.; Melchiorre, P.; Sambri, L. Synlett 2004, 1794.
[8] Bartoli, G.; Bosco, M.; Locatelli, M.; Marcantoni, E.; Melchiorre, P.; Sambri, L. Org. Lett., 2004, 7, 427
Simultanea determinazione mediante square wave anodic stripping voltammetry di "platinum group metals (PGMs)" e Pb in matrici ambientali
No full textIl presente lavoro, riguarda la determinazione di Pt(II), Pd(II), Rh(III) e Pb(II) mediante voltammetria di ridissoluzione anodica ad onda quadra (SWASV).
La procedura analitica è stata verificata mediante l’analisi di materiali standard di riferimento.
La precisione e l’accuratezza, espresse rispettivamente come deviazione standard relativa ed errore relativo, sono risultate inferiori al 6 % in tutti i casi.
Viene valutata la possibilità di usare l’area di picco come parametro strumentale1. Sono valutate inoltre le possibili interferenze2. Una volta messa a punto su soluzioni acquose di riferimento e verificata su materiali standard di riferimento, la procedura analitica proposta è stata trasferita ed applicata su campioni reali prelevati in ecosistemi diversamente influenzati dal traffico veicolare.
Nel presente lavoro viene anche discusso un confronto critico con misure spettroscopiche effettuate sugli stessi campioni.
1. C. Locatelli, C. Electroanalysis 2003, 15, 1397-1402.
2. C. Locatelli, C.; G. Torsi, G. J. of Electroanal. Chem. 2001, 509, 80-89
APPLICATIONS OF PERCHLORATES IN ORGANIC SYNTHESIS. A NEW AND GENERAL ROUTE TO t-BUTYL ETHERS
No full textAPPLICATIONS OF PERCHLORATES IN ORGANIC SYNTHESIS. A NEW AND GENERAL ROUTE TO t-BUTYL ETHERS
Giuseppe Bartoli, Marcella Bosco, Manuela Locatelli, Paolo Melchiorre and Letizia Sambri
Dipartimento di Chimica Organica “A. Mangini”, v.le Risorgimento 4, Bologna, Italy
[email protected]
In the last few years, we were interested in the use of various metallic perchlorates as Lewis acid promoters in various organic transformations.1 In particular, perchlorate salts have shown a high ability to activate 1,3-dicarbonyl systems.
We surprisingly found that anhydrous Mg(ClO4)2 promotes the reaction of alcohols with t-butyl dicarbonate (Boc2O) to give t-butyl ethers.2 This reaction appears extremely interesting, as it represents a potential solution to a longstanding problem in organic synthesis namely, t-butyl ether formation. The t-butyl ether in fact is “one of the most underused alcohol protecting groups”,3 although it is one of the few ethers stable under strongly basic conditions.
We set up a new protocol for the synthesis of t-butyl ethers from a large variety of functionalized aromatic and aliphatic alcohols. Selective mono-protection of symmetric and asymmetric diols can also be achieved.
At the same time, a convenient deprotection protocol was set up. In fact, t-butyl ethers were easily reconverted in the corresponding alcohols by simple treatment with the CeCl3/NaI system.4
Scheme 1.
1. Bartoli, G.; Boeglin, J.; Bosco, M.; Locatelli, M.; Massaccesi, M.; Melchiorre, P.; Sambri, L. Adv. Synth. Catal. 2005, 347, 33-38. and references herein cited.
2. Bartoli, G.; Bosco, M.; Locatelli, M.; Marcantoni, E.; Melchiorre, P.; Sambri, L. Org. Lett. 2005, 7, 427-430.
3. Greene, T. W.; Wuts, P. G. M in Protective Groups in Organic Synthesis, Wiley, New York, 3rd Ed., 1999, pp. 65-67.
4. Bartoli, G.; Marcantoni, E.; Sambri, L. Synlett, 2003, 2101-2116
CAP4KAM_nDOF: Computer-Assisted Proofs of existence of KAM tori in Hamiltonian systems with n (>=2) Degrees Of Freedom
No full textIn the folder you can produce by uncompressing the attached zippedfile (namely, that folder is called "CAP4KAM_nDOF"), you should findeverything you need in order to perform a complete computer-assistedproof of existence of invariant tori for a Hamiltonian that satifiesthree assumptions: (i) it describes a (Hamiltonian) system with n>=2 degrees of freedom and its canonical coordinates are n pairs of action-angle variables; (ii) it is close enough to a Kolmogorov normal form (so fulfilling also both the non-resonance and the non-degeneracy conditions usually adopted in the framework of KAM theory); (iii) its expansion in Taylor series (with respect to the actions) is finite, while its Fourier expansions (in the angles) can be infinite.The software included in the present folder "CAP4KAM_nDOF" is anextension of a first public release that was a sort of supplementarymaterial of the paper [VL], i.e.,Locatelli, Ugo (2021), “CAP4KAM2D: Computer-Assisted Proofs Fordemonstrating the existence of 2-Dimensional KAM tori”, MendeleyData, V1, doi: 10.17632/jdx22ysh2s.1The software included in the folder "CAP4KAM_nDOF" is designed tobe in a "easy-to-use" layout. Moreover, it is probably not too difficultto be modified for people expert in programming (in C).Everything about the files included in the folder "CAP4KAM_nDOF" iswidely described in the README.txt, that contains also carefulexplanations that should be useful for running the codes, monitoringthe results, modifying the input files, etc.Eventual corrections or remarks about the software package includedin the folder "CAP4KAM_nDOF" are more than welcome and can besent to the author (Ugo Locatelli) at the following e-mail address: [email protected]
Jean Tardieu, père et artiste. Entretien avec Alix Turolla-Tardieu
No full textInterview of Alix Turolla-Tardieu, the daughter of the poet and author Jean Tardieu
UNITY-Locatelli Meeting Notes
No full textTyped document titled 'UNITY-Father Locatelli Meeting 4/14/89.' Document includes five numerical bullets with agenda items the include an introduction/welcome; history of UNITY; information regarding UNITY "today"; demands; and a session titled 'Open for discussion.' Documents features handwritten notes in black ink. Document does not specify author of agenda or notes
The Dark Side of Projects: Uncovering Slavery, Corruption, Criminal Organizations, and Other Uncomfortable Topics
No full textUnethical and illegal practices abound in our modern world. For
example, slavery in several countries was abolished at the turn
of the nineteen century, yet, at this very moment, approximately
40 million people worldwide are considered to be modern
slaves (International Labour Organization [ILO] & Walk Free
Foundation [WFF], 2017), more than three times the entire
Atlantic slave trade. The extent of corruption is equally shocking and costs society US$3.6 trillion globally in the forms of
bribes and stolen money (Johnson, 2018), roughly Germany’s
GDP, the fourth highest in the world. The two examples are
just the tip of the iceberg; the business world has dark stains,
and projects are no exception. For instance, construction projects employ modern slaves (Amnesty International, 2021;
Gulf News, 2019; Pattisson et al., 2021), are involved in corruption scandals (Lehtinen et al., 2022; Olken, 2007, 2009), and are
sometimes used for money laundering (Locatelli et al., 2022).
The dark side of projects, that is, “any illegal, or unethical phenomena associated with projects” (Locatelli et al., 2022), as
those exemplified above, is real, relevant, and merits further
investigation
Diversidade de minhocas e atributos químicos em sistemas de plantio direto e integração lavoura-pecuária do oeste catarinense.
No full textResumo também apresentado no CONGRESSO DE INICIAÇÃO CIENTÍFICA E PÓS-GRADUAÇÃO, 2., 2012, São Leopoldo. Mostra de iniciação científica da UNISINOS. São Leopoldo: Casa Leiria, 2012. e-book. II CICPG. Disposição dos autores: ORSO, R.; BARTZ, M. L. C.; BROWN, G. G.; KLAUBER FILHO, O.; ROSA, M. G. da; LOCATELLI, M.; ZORTÉA, T.; CASAROTTO, K.; DECÄENS, T.; BARETTA, D
Elettrodi a diffusione di gas per idrodealogenazione elettrocatalitica su argento di composti organici volatili policlorurati
No full textElettrodi a diffusione di gas per idrodealogenazione elettrocatalitica su argento di composti organici volatili policlorurati.
Alberto Vertova,* Gabriele Aricci, Cristina Locatelli, Carlo Pirola, Sandra Rondinini
Dipartimento di Chimica Fisica ed Elettrochimica, via Golgi 19 – 20133 Milano
*e-mail: [email protected]
Gli alogenuri organici volatili rappresentano una delle categorie di inquinanti organici più difficilmente trattabili per la loro elevata tossicità. Queste sostanze essendo dotate di forte resistenza a trattamenti fisici, chimici e biologici si accumulano facilmente nell’ambiente e possono entrare a far parte della catena alimentare.[1] Grande importanza assume quindi lo studio di metodi validi, efficaci ed economicamente sostenibili per la degradazione di tali substrati. Tra i diversi tipi di trattamenti, i processi riduttivi sono particolarmente interessanti perché i prodotti finali ottenibili sono idrocarburi a basso peso molecolare, ad esempio il metano. In particolare, i processi di degradazione riduttiva elettrolitica su elettrodi a base di argento dei composti citati costituisce un processo innovativo molto promettente.[2]
In questa presentazione vengono discussi i risultati di un processo elettroriduttivo con Gas Diffusion Electrode (GDE) a base di argento su molecole organico modello quali il triclorometano e l’1,1,1-tricloroetano, alimentate alla cella tramite un gas inerte.
Lo studio ha previsto due tipi di prove: misure potenziodinamiche, per caratterizzare i GDE in diversi ambienti di reazione; elettrolisi preparative, per verificare il meccanismo di reazione tramite l’analisi dei prodotti gassosi in uscita dalla cella. Nel secondo caso si è proceduto sia con l’impiego di una cella divisa che con cella indivisa, ponendo particolare attenzione all’elettrolita utilizzato.
La degradazione elettroriduttiva del CHCl3 ha portato prevalentemente a metano e in misura minore a prodotti di parziale dealogenazione; nel caso del’1,1,1-tricloroetano il prodotto principale è etano, con tracce di etene e di prodotti di parziale dealogenazione.
[1] C. Costentin, M. Robert, J.M. Seveant, J. Am. Chem. Soc., 125 10729 (2003)
[2] G. Fiori, S. Rondinini, G. Sello, A. Vertova, M. Cirja, L. Conti, J. Appl. Electrochem. , 35 363 (2005
Teaching sustainable energy systems to engineering students
No full textThis paper presents the learning outcomes, syllabus, delivery, and assessment strategy for a module of 'Sustainable energy systems' for master-level engineering students. The paper is based on three stages of 'action research'. The first stage is a critical reflection on the planning and the process, based on the experience in delivering the original module and literature review. The second stage is based on semi-structured interviews of 4th-year students, focused on the collection of feedback to improve the module. The third stage is the redesign and peer-review of the module. The key outcome of this work is an approach which further enables students to move from 'surface learning' to a more profound 'deep learning'. Further steps forward toward a true 'constructivism' are also envisaged. Several enhancements are discussed, including an improved syllabus, new methods of delivery, fine-tuning of the learning outcomes, and finally revisiting the assessment strategy
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