UNIFIED TOPOLOGY OF FRONTIER MOLECULAR ORBITALS TO EXPLAIN PERICYCLIC REACTIONS

<p></p><p>In this work is proposed a didactic alternative vision to teach pericyclic reactions. To this end, they were classified according to the connectivity of reactants systems, as connected atom reactions (CAR) and the other possibility, as not connected atom reactions (NOCAR). Electrocyclic reactions and sigmatropic rearrangements are examples of CAR categorization, and the cycloadditions being NOCAR. With these two categories, a pedagogical alternative description is proposed to the orbital topology in reactants to explain the pericyclic reactions. According to this classification, the HOMO's topology is adequate to all CAR, while the traditional HOMO-LUMO's topology is adequate to NOCAR. All issues typically deduced by the traditional treatment, such as allowed and forbidden reactions, and stereochemical aspects are also explained by the alternative approach.</p><p></p

TOPOLOGY OF MOLECULAR ORBITAL FOR DEDUCING RELATIVE ENERGIES FROM POLYENE AND EVALUATING AROMATICITY

<p></p><p>A didactic alternative approach is proposed for deducing the molecular orbital topology of acyclic and cyclic polyenes and then evaluating their bonding, antibonding, and nonbonding character. The relative energies of molecular orbitals of neutral molecules and ions were described, in addition to the orbital degeneracy to cyclic conjugated polyenes, and the method deduce correctly the relative stability of polyenes. This alternative method complements the lack of explanation of a substantial number of organic chemist undergraduate textbooks in relation to orbital degeneracy in benzene and is a pedagogical approach to teach aromaticity and antiaromaticity.</p><p></p

BEYOND CAIPIRINHA: BRAZILIAN CACHAÇA AS SOLVENT TO ORGANIC SYNTHESIS AND DYE EXTRACTION

<p></p><p>Cachaça (brazilian sugarcane spirit) was applied for the first time as an alternative solvent in undergraduate experiments of organics synthesis, and natural dye extraction. The classical Claisen-Schmidt condensation of benzaldehyde with acetophenone and with acetone were employed to demonstrate the cachaça viability as solvent. Cachaça was also the recrystallization solvent of obtained benzalacetophenone and dibenzalacetone. The natural pigment of urucum (Bixa orellana L.) was obtained using as extractor solvent a 5% NaOH solution in cachaça. Considering that in Brazil cachaça is easily available and cheaper than the 40% mixture of ethanol/water, it can be found in every marketplace and is exported to 54 countries, the cachaça use as solvent is viable and attractive to green chemistry experiments in undergraduate courses, in Brazil and abroad.</p><p></p

MECHANOCHEMICAL CHLORINATION OF ACETANILIDE

<p></p><p>We described herein a solvent-free synthesis of 4-chloroacetanilide both under hand grinding and mechanical grinding of stoichiometric amounts of acetanilide with trichloroisocyanuric acid. The synthetic approach was developed in the context of undergraduate organic chemistry and is the greener preparation of this compound already described.</p><p></p

AVOCADO, SPENT COFFEE GROUNDS, LICURI AND COCONUT MILK FOR OIL EXTRACTION, BIODIESEL PRODUCTION, AND SPECTRAL ANALYSIS

<p></p><p>An undergraduate organic chemistry experiment for oil extraction and biodiesel production using alternative biomass was developed, whereby oils of avocado, coconut and spent coffee grounds were obtained and submitted to transesterification reaction with CH3OH under NaOH catalysis. Avocado and coffee oils were obtained by typical extraction and coconut oil was obtained through water evaporation of coconut milk in a domestic microwave oven. The commercial oil of licuri (Syagrus coronate), a Brazilian native biomass, was also converted to biodiesel. All four oils and four biodiesels were characterized by 1H-NMR and FTIR, and a comparative study of these spectra reveled that FTIR analyses alone provides enough information to discriminate between oil and biodiesel and confirm transesterification reaction. Besides, the unsaturation degree of all oils was determined by 1H-NMR. A mechanistic proposal concerning the role of NaOH catalysis is presented, excluding the sodium methoxide formation.</p><p></p