Experiment 3

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Feb 20, 2024

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Experiment 3: Molecular Modeling in Organic Chemistry Molecular Polarity and Chromatography Alexander Filosa Department of Chemistry, Binghamton University, Binghamton, NY, 13902 October 30, 2022 Post Lab Exercise: 1) Overall, which of the three molecules is the most polar – widest separation of positive and negative charge – and least polar?  Through the molecular modeling of each molecule – sulfide, sulfone and sulfoxide – it was found that the most polar is to be sulfone. Sulfone is the most polar due to the fact it has the largest electronegativity difference between the sulfur and oxygen. Whereas, though, sulfide is the least polar due to there being little to no difference in polarities of the carbon and oxygen. 2) Considering only the functional group in each molecule, which atom(s) are most positively charged, and which is/are most negatively charged? – Use data obtained in the activity to support your answer.  Considering only the functional group in each molecule it was found that the atom that is mostly positively charged is the carbon atom. When looking at the electrostatic map, it is shown the carbon is mostly electropositive making it the positively charged atom. And, with oxygen being highly electronegative, it is mostly a negative charge. 3) Looking at the reaction and charge distribution data obtained for the three components, does increased oxidation lead to sulfur being positively or negatively charged? Or does it leave sulfur unchanged?  Looking at the reaction and charge distribution data obtained for the three components the increased oxidation of sulfur leads it to be more positively charged rather than negatively charged. 4) On the electrostatic potential maps, indicate electrophilic and nucleophilic regions of each component of this oxidation reaction.  When looking at an electrostatic potential map, the electrophilic center is the sulfur molecule due to it being positively charged. The nucleophilic center is oxygen due to it being negatively charged. 5) Suppose this reaction’s crude mixture is dissolved in a solvent and spotted on a silica- coated TLC plate and developed using an appropriate solvent. Which compound would you expect to elute first, and which would elute last? Use the data obtained in this activity portion and knowledge of the TLC technique to explain your reasoning.  If this reaction’s crude mixture is dissolved in a solvent and spotted on a silica-coated TLC plate along with being developed with the appropriate solvent, polarity is used to determine which molecule would elute first. More specifically, the most polar would elute first. And, in this case, the sulfone molecule is predicted to elute first as it is the most polar molecule out of the three.

Analysis: When there is an existence of a diploe, there also exists a separation of both the positive and negative charges. The electronegativity of these atoms being adjourned leads to covalent bonds either polar or nonpolar. Dipole moments, though, only occur when there is polarization. Symmetry also plays a factor in the dipole moment. So, by using computation methods, such as building 3-D models of these molecules to help visualize how a molecule looks like; find their molecular geometries; determine their dipole moment and atomic charges and help create an electrostatic map for each molecule. With the 3-D model being at hand showing the electrostatic map concurrently, finding which molecule was most polarized or which molecule had positive or negative charges was easy. The sulfide had a dipole moment of 1.718422 debeye; the sulfoxide had a dipole moment of 3.952369 debeye; and the sulfone had a dipole moment of 4.569959 debeye. The partial charges for the atoms in the sulfide functional group are -0.59 on the carbon (fifth carbon atom), 0.08 on the sulfide and -0.22 on the carbon (second carbon atom) as the group is an angular group approaching a 90-degree angle. For the partial sulfoxide group, the sulfide is 0.76, the oxygen is -0.64 ( the third oxygen atom) and carbon 4 is -0.27, and carbon 2 is -0.63. For the partial charge of sulfone, it is 1.11 on the sulfide, -0.54 and -0.55 on the two double bonded oxygen (seventh and eighth oxygen atoms respectively) and .20 on the 16 th hydrogen atom, and .18 on the 11 th hydrogen atom. The findings show that sulfone is the most polar and sulfide is the least polar. This all relates to the scientific purpose of this experiment as models of molecules were analyzed as well as their properties such as dipole moment, partial atomic charges and electrostatic potential map(s). These findings would help to show which molecules would elute first in an experiment since the more polar a molecule is, the faster it

elutes. If there are any contradictions with any of the findings, a second trial of creating 3-D models could be done to resolve these contradictions. Citation: Fall 2022 Chemistry 335 Organic Chemistry Lab Course Companion  Sulfide  sulfone

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