Lone Pairs: An Electrostatic Viewpoint

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1 S1 Supporting Information Lone Pairs: An Electrostatic Viewpoint Anmol Kumar, Shridhar R. Gadre, * Neetha Mohan and Cherumuttathu H. Suresh * Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur , India Inorganic and Theoretical Chemistry Section, Chemical Sciences and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum , India Table of Contents Table S1: MESP topography features of molecules bearing lone pairs and those containing other electron localizations. Table S2: MESP topography features of molecules bearing both lone pairs and π bonds. S2 S3 Figure S1: Representation of MESP topography of a set of molecules showing location of (3,+3) CP s(red) with respect to their van der Waals surface. Table S3: Comparison of NBO and ELF features of H 2 O, CH 3 NH, OCH 3 and furan. Lone pairs in cations Figure S2: HOMO of H 3 O + Figure S3: Complexes of hydronium ion with BH 3 and NH + 4. S3 S4 S5 S5 S6

2 S2 Table S1. MESP topography features of molecules bearing lone pairs and those containing other electron localizations, listing the number of distinct negative-valued minima, distance of the minimum from nearest atom, Value of MESP (V min ), and the largest eigenvalue (LE) (all values in a.u.). The angle made by eigenvector (corresponding to LE) with the position vector joining nearest atom to CP is also provided. See text for details. Molecules No. of distinct CPs Distance V min LE Angle ( ) H 2 O N NH H 2 CO H 2 S HCN CH 3 OH O(CH 3 ) OH OCH CH 3 NH CH 3 CO NO 3 - H 2 PO Methane Benzene Butadiene Cyclobutane Cyclopropane Ethane Diborane

3 S3 Table S2. MESP topography features of molecules bearing both lone pairs and π bonds. Notation identical to that of Table S1. Molecules No. of distinct CPs Distance V min LE Angle ( ) Imidazole Pyrazine Furan Pyridine Pyrimidine Borazine PH Figure S1. Representation of MESP topography of a set of molecules showing location of (3,+3) CP s(red) with respect to their van der Waals surface.

S4 Table S3: Comparison of NBO and ELF features of H 2 O, CH 3 NH, OCH 3 and furan a.

Molecules NBO ELF OCH 3 H 2 O CH 3 NH Furan a Quantum chemical calculations were performed

But density was built at HF level in case of NBO analysis and ELF.

in the cases studied and also percentage participation of s and p orbitals in making up a

location of the lone pairs. Rather, it shows the occupancy in localized MO.

values at attractors do not correlate with lone pair strength.

4 S4 Table S3: Comparison of NBO and ELF features of H 2 O, CH 3 NH, OCH 3 and furan a. See footnote for details. Molecules NBO ELF OCH 3 H 2 O CH 3 NH Furan a Quantum chemical calculations were performed on simple molecules like H 2 O, CH 3 NH, OCH 3 and furan to see whether NBO and ELF pictures differs or matches with MESP. The level of theory and basis was same for all the calculations. But density was built at HF level in case of NBO analysis and ELF. It was observed that NBO analysis makes correct predictions about the number of lone pairs in the cases studied and also percentage participation of s and p orbitals in making up a particular lone pair, matching hybridization concepts but fails to predict the geometrical location of the lone pairs. Rather, it shows the occupancy in localized MO. ELF shows expected geometrical location of the lone pairs in H 2 O, CH 3 NH, OCH 3 but the values at attractors do not correlate with lone pair strength. In case of furan, ELF shows two lone pairs on oxygen, which are tetrahedrally disposed about the plane of the ring. This alignment contradicts with MESP description as well as resonance concepts. Resonance needs orbitals to be in plane perpendicular to the ring thus it is expected that one lone pair delocalize over the ring and other lies in plane of ring as shown by MESP topography. In addition, according to literature (J. Phys. Chem. A, 2000, 104, ), ELF is very sensitive to basis set

5 S5 which causes unexplained localization of excess kinetic energy of electrons in certain anionic hydrides. More than that aim to distinguish lone pair from other electron localizations has not been touched by other methods. Lone pairs in cations The orbital picture of H 3 O + shows that HOMO represents the lone pair orbital (Figure S2). The HOH angle of H 3 O + is o suggesting a deviation of 2.7 o from the typical o for a sp 3 hybridized system. Compared to the HOH angle of o for H 2 O, a large deviation 7.7 o is observed for H 3 O +. These results suggest that the lone pair orbital is not purely 'non-bonding' in nature and it provides some amount of bonding interaction with the three hydrogen atoms. Figure S2: HOMO of H 3 O + The HOMO does not show a tendency to donate the lone pair to an electron deficient molecule like BH 3. Calculations show that formation of H 3 O +...BH 3 donor-acceptor complex is not favoured and instead a dihydrogen bonded complex (Figure S3 (a)) is formed. This result indicates that H 3 O + behaves as if it has no lone pair on oxygen. If a lone pair exists in H 3 O +, formation of H 3 O + H 3 N can be expected with hydrogen of the ammonia interacting with the lone pair on oxygen. Calculations show that such a complex does not exist and the optimization leads to the formation of H 2 O NH + 4 complex. In this cationic complex, two lone pairs can be expected for H 2 O as there is no chance to donate electrons from H 2 O to NH + 4. MESP shows these two lone pairs (Figure S3 (b)).

6 S6 LP of H 2 O (a) (b) (c) Figure S3: (a) Intermolecular dihydrogen bond complex between H 3 O + and BH 3 (b) H 2 O NH 4 + complex. (c) MESP isosurfaces showing lone pairs on H2O molecule in H 2 O NH 4 + complex.

SL Score. HL Score ! /30 ! /48. Practice Exam: Paper 1 Topic 4: Bonding. Name

SL Score. HL Score ! /30 ! /48. Practice Exam: Paper 1 Topic 4: Bonding. Name Name Practice Exam: Paper 1 Topic 4: Bonding SL SL Score! /30 HL Score! /48 1. What is the correct Lewis structure for hypochlorous acid, a compound containing chlorine, hydrogen and oxygen? A. B. C. D.