ECTP2014 - 20th European Conference on Thermophysical Properties Poster P_130, 3 Sept. 15:30 – 19:00 EXPERIMENTAL AND COMPUTATIONAL INSIGHTS ON THE TERMOCHEMISTRY OF 1-ETHYL2-R-INDOLE DERIVATIVES (R = METHYL, PHENYL) Tânia M. T. Carvalho1; Luísa M. P. F. Amaral1; Victor M. F. Morais2; Maria D. M. C. Ribeiro da Silva1 Centro de Investigação em Química da Faculdade de Ciências da Universidade do Porto, Portugal; de Investigação em Química da Faculdade de Ciências da Universidade do Porto; Instituto de Ciências Biomédicas da Universidade do Porto, Portugal. 1 2Centro The large number of scientific publications in different areas of knowledge related with the indole derivatives is an obvious acknowledgement of their importance. This happens since indole is a very important building block for naturally occurring compounds and also as an intermediate in the manufacture of synthetic chemicals. Indole is also the sidechain chromophore of the amino acid tryptophan, and, therefore, it is important to understand its properties in the excited-state in order to have an accurate interpretation about the luminescence and absorption spectra of the mentioned amino acid. In the sequence of our previous study [1,2], we are involved in the study of influence of the substituent (alkyl or aryl) in the position 2 on the 1-ethylindole structure (Figure 1). In this work, the standard (po = 0.1 MPa) molar energy of combustion, of 1-ethyl-2-methylindole, in the crystalline state, was determined, at T = 298.15 K, using a static bomb combustion calorimeter.The standard molar enthalpy of vaporization, at T = 298.15 K, was determined by Calvet microcalorimetry. From the experimental results, the standard (po = 0.1 MPa) molar enthalpy of formation of the compound, in the condensed and gaseous phases, at T = 298.15 K, were derived. The result obtained for the gaseous enthalpy of formation has been compared with the previous one reported for 1-ethyl-2-phenylindole . Additionally, theoretical calculations was performed using density functional theory (DFT) with the hybrid functional B3LYP together with the 6-31G(d) and the 6-311+G(2df,2p) basis sets.With the objective of assessing the quality of the results, standard ab initio molecular orbital calculations at the G3(MP2) level were also performed. Enthalpies of formation, obtained using appropriate working reactions, were calculated and compared with experimental data. Figure 1: Structural formula of the compounds under study Acknowledgments: Thanks are due to FCT, Lisbon, Portugal, and European Social Fund for financial support given to CIQ-UP, strategic project PEst-C/QUI/UI0081/2013. LMPF Amaral holds a Ciência 2008 position of the Portuguese Ministry of Science.  Energetic study of 1-R-2-Phenylindole (R=H, CH3, C2H5), Carvalho, T. M. T.; Amaral, L. M. P. F.; Ribeiro da Silva, M. D. M. C., 11º Encontro Nacional de Química-Física, Porto, Portugal, 9 -10 May 2013.  Experimental and computational energetic study of 1-R-2-phenylindole (R=H, CH3, C2H5), T. M. T.; Amaral, L. M. P. F.; Ribeiro da Silva, M. D. M. C., 4PYCHEM, Coimbra, Portugal, 29 April – 1 May 2014.