A Simple Concept of Color Forming in Common Compounds That Find on Senior/Vocation High School Level with Computational Approach Ajeng Nega Reni Damayanti 1,3 Aristia Pratiwi Meliawati 2,4 Nur Azlina Oktavianti 1,5 and Badra Sanditya Rattyananda 2,6,*
1.Master Program of Teaching Chemistry, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology
2. Master Program of Chemistry, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology
3. 1 State Islamic Senior High School (MAN 1) in Trenggalek
4. 6 State Vocational High School (SMKN 6) in Garut
5. 1 State Vocational High School (SMKN 1) in North Tambusai - Rokan Hulu
6. National Research & Innovation Agency of Indonesia
From KBBI, color was defined as the impression that eye gets from the light reflected by objects it hits. In chemistry, color was obtained from the excitation of electrons from the ground state (HOMO) to an empty orbital that was one energy level above (LUMO). The energy required for this excitation process was proportional to the wavelength of visible light in the range of 380-740 nm. For Senior / MA / vocational high school students this concept was a bit difficult to imagine, therefore computing was here to make it easier for students to understand it. The compounds chosen to represent the red color were Lycopene from tomatoes, orange color from β--carotene from carrots, yellow color from Tartrazine, green color from chlorophyll, blue color from phycocyanin obtained from spirulina, and purple color from anthocyanins strain from potatoes. The six compounds were calculated computationally with ORCA 5.0.3 software using DFT method with Hybrid-GGA B3LYP functional and 2nd generation of Ahlrichs basis sets def2-SVP. Guess structure was optimized that the result becomes as input of Single point energy and UV-Vis prediction spectrum. The all energy of the transition from HOMO to LUMO were obtained that was on visible frequency range. It result corresponds to the concept of complementary colors that produce the colors human see. Thus, the result of orbitals with computational approach hoped to make students will be able to understand formed colors better. Furthermore, the concept of a computational approach with more complicated methods such as EOM-CCSD (Equation of Motion-Coupled Cluster Singles and Doubles) can be used to explain the concept of secondary and combined color more accurately.
Keywords: Color, HOMO (Highest Occupied Molecular Orbital), LUMO (Lowest Unoccupied Molecular Orbital), Complementary Color Concepts, UV Absorption
