Emeritus Faculty Member

Mail: Chemistry & Chemical Biology, 610 Taylor Road, Piscataway, NJ 08854

Education

• B.S. 1953, Pennsylvania State University
• Ph.D. 1956 University of Illinois
• Post Doctoral 1957 University of Illinois

Awards & Honors

• NIH Postdoctoral Fellowship University of Illinois: 1956
• NIH Special Fellow, Princeton University: 1967
• NIH Special Fellow, Brandeis University: 1972

Research Summary

My interests deal with solving mechanistic and structural problems in organic chemistry using modern quantum mechanical methodology. Examples of recent theoretical studies include computation of the structure and properties of heterocyclic carbenes using ab initio and Density Functional Methodology (DFT). We have computed thermochemical properties and magnetic resonance ring current effects to probe the aromaticity of cyclic carbenes that contain 6-pi electrons. There is evidence for significant aromatic stabilization if at least two nitrogen atoms are part of the pi system in the ring. When oxygen or sulfur is part of the cycle the stabilization is greatly reduced. Conformational studies of bridging by halogens in 2-halo cations have revealed systematic dependency on halogen vs charge density.

Computaional Studies of Carbon Atom Complex Formation

Recent computational studies on complexation of atomic carbon atoms with pi-systems has revealed a remarkable series of complexes with molecules with at least two conjugated pi-bonds, e.g., the singlet state of cyclopentadienylidine. The complexes are stabilized by as much as 154 kcal/mol relative to uncomplexed componentts. The computed natureal charges on the lone carbon atom are consistently ~0, and the complexes have significant dipole moments more or less in the plane of the pl-system.  Wiberg bond orders between carbon and the ring atoms areare significant, with totals up to 2.6. 

Single Electron Transfer

A comprehensive study of the SN2 reaction in the gas phase with a variety of nucleophiles has revealed a remarkable correlation between the computed transition structure energies and the ionization potential of a series of nucleophiles over a range of 14 Ev. No correlations were found between proton affinities or ionization potentials and central barrier heights.  In addition some unusual reversals of primary vs  secondary reactivity were found.   The generality of these results is under investigation.

Hyperfine Splitting

We are using Natural Bond Orbital theory to analyze the dependency hyperfine splitting of protons on geometry and other spatial parameters. A series of rigid cyclopropyl radical cations and organic radicals serves as the framework.

NBO Methodology applied to radicals and carbanions

Natural bond orbital methodology is used to provide insights into detailed distribution of charge and the importance of hyperconjugation in aliphatic and alicyclic radicals and carbanions.

Analysis of Substituent Effects on Singlet Carbene Stability

We have computed the relative stabilities of a large number of X-sustltuted carbenes and are analyzing the results by multifple linear regression analyses in an attempt to define the relative importance of field vs resonance effects. Our findings suggest that substituent effects cannot be correlated by typical Hammett methods due to synergism between substituents.

Collaborative Studies

Collaborative studies include computational studies of fragmentation reactions of oxychlorocarbenes, structures of halonium ions, the mechanism of alkyl azide/thioacetate reactions, long range spin properties and reactions of radical cations,  properties of natural and un-natural base pairs, mechanisms of reverse Diels- Alder  reactions, NMR  properties of bridgehead alkenes. We have been applying natural bond orbital methodology to analyze conformational preferences of various ions and molecules. Finally, a major computational analysis of the structure and reactivity of bis-quaternary ammonium ion pairs in the gas phase  has revealed novel relationships between substitution  reactions and nucleophilicity.  We have revealed a reasonable mechanism for the formation of diazacyclopropenone from the decomposition of a Meisenheimer complex.  More recent studies have involved computational studies of binding energies of halide ions with bis-quaternary ammonium salts as part of a program designted to study the Hofmeister erffect.

Publications

1. Sauers, R. R. "Theoretical study of reactions of atomic carbon with some π-systems" Comp Theo Chem. 2015,1056, 19-23.
2. Sauers, R. R. "Singlet carbene stability: linear free energy analysis of substitutent effects" ARKIVOC, 2014 (v), 376-383.
3. Roth, H. D.; Sauers, R. R.; "Approach to Loschmidt’s Tetracyclic Benzene Isomer and Related Tetra- and Tricyclic Isomers by Intramolecular Carbene Additions " J. Phys. Org. Chem. 2015:  DOI: 10.1002/poc.3391.
4. Roth, H. D.; Sauers, R. R.; Theisen, K. J. Neshchadin, D,; Gescheidt, G. "Radical Cations of Disubstituted Cyclopanes: Stereoelecctronic Effects on Hyperfine Coupling" J. Phys. Org. Chem. 2014: DOI: 10.1002/POC 3269.
5. Roth, H. D.; Sauers, R. R. "Triplet recomibination of radical ion pairs: CIDNP effects and DFT calculations on 1,2-dicyanoethylene" Photochem Photobiol Sci. 2013: DOI: 10.1039/C3PP50313A.
6. Roth, H. D.; Sauers, R. R. "Radical cations and triplet states of 1,2-disubstituted cyclopropanes: comparison of potential surfaces" Photochem Photobiol Sci. 2012, 11, 931-937.
7. Sauers, R. R. "A natural bond orbital analysis of carbanions" Comp Theo Chem. 2012, 43-47.
   
8. Sauers, R. R. "A natural bond orbital analysis of hydrocarbon radicals" Comp Theo Chem. 2011, 970, 73-78.
9. Moss, R. A.; Lu, Z.; Sauers, R. R. "Triplet halocarbene chemistry: p-nitrophenylchlorocarbene and p-nitrophenylbromocarbene" Tetrahedron Lett. 2010, 51, 5940-5942.
10. Sauers, R. R. “Single Electron Transfer and the SN2 Reaction: The Importance of Ionization Energy of Nucleophiles” J. Chem. Theory Comput. 2010, 6, 602-606.
11. Moss, R. A.; Sauers, R. R. “The Generation of Diazirinone: a Computational Study” Tetrahedron Lett.  2010, 51, 3266-3268.
12. Lu, Z.; Moss, R. A.; Sauers, R. R.; Warmuth, R. “Innermolecular Reactions of Fluorophenylcarbene inside a Hemicarcerand” Org. Lett. 2009, 17, 3866-3869.
13. Srinivasan, A. R.; Sauers, R. R.; Fenley, M. O.; Boschitsch, A. H.; Matsumoto, A.; Colasanti, A. V.; Olson, W. K. “Properties of the nucleic-acid bases in free and Watson-Crick hydrogen-bonded states: computational insights into the sequence-dependent features of double-helical DNA” Biophys Rev. 2009, 1, 13-20.
14. Aime, C; Plet, B.; Manet, S.; Schmitter, J-M.; Huc, I.; Oda, R.; Sauers, R. R.; Romsted, L. S. “Competing Gas-Phase Substitution and Elimination Reactions of Gemini Surfactants with Anionic Counterions by Mass Spectrometry. Density Functional Theory Correlations with Their Bolaform Halide Salt Models” J. Phys. Chem. B 2008, 112, 14435-14445.
15. Regler, B.; Emge, T. J.; Elliott, J. J.; Sauers, R. R.; Potenza, J. A.; Romsted, L. S. “Structural, Infrared, and Density Functional Theory Studies of N,N,N’,N’-Tetramethylimidazolidinium Dichloride. A Model for Cation-Anion Association of Headgroups and Counterions in the Interfacial Regions of Gemini Micelles” J. Phys. Chem. B 2007, 111, 13668-13674.
16. Lotesta, S.D.; Kiren, S.; Sauers, R. R.; Williams, L. J. “Spirodiepoxides: Heterocycle Synthesis and Mechanistic Insight” Angew. Chem. Int. Ed. Engl. 2007, 46, 7108-7111.
17. Haubenstock, H.; Sauers, R. R. “NBO Analysis of Halogen Bridging in 4-Halo-1-buten-3-yl Cations” Journal of Molecular Structure: THEOCHEM 2007, 822, 8-11.
18. R. A. Moss; J. Tian; R.R. Sauers; C. Skalit, K. Krogh-Jespersen; "Chlorofluorocarbene: First UV Observation of a Dihalocarbene in Solution," Organic Lett., 2007, 9, 4053
19. R.A. Moss; J. Tian; R.R. Sauers; K. Krogh-Jespersen; "Tracking "Invisible" Alkylchlorocarbenes by Their Sigma to Pi Absorptions: Dynamics and Solvent Interactions," J. Am. Chem. Soc., 2007, 129, 10019.
20. R.A. Moss; J. Tian; G. Chu; R.R. Sauers; K. Krogh-Jespersen,"New Mechanisms Centered on Reactive Intermediates: Examples from Diazirine and Carbene Chemistry," Pure Appl. Chem., 2007, 79, 993.
21. R.A. Moss; X. Fu; R.R. Sauers; "SNi Fragmentations of Alkoxychlorocarbenes - A Perspective," J. Phys. Org. Chem., 2007, 20, 1.
22. R.A. Moss; J. Tian; R.R. Sauers; D.H. Ess; K.N. Houk; K. Krogh-Jespersen,"The Synthesis of Dichlorodiazirine and the Generation of Dichlorocarbene: Spectroscopy and Structure of Dichlorocarbene-Ylides," J. Am. Chem. Soc, 2007, 129, 5167.
23. Moss; L. Wang; R.R.Sauers,"Presumptive Evidence for an Intermediate Oxirane in the Reaction of Phenylfluorocarbene with Cyclohexenone," Tetrahedron Lett., 2007, 48, 5551.
24. Goodman, L.; Sauers, R. R. “Diffuse Functions in Natural Bond Orbital Analysis”, J. Comp. Chem. 2006, 1, 1185-1192.
25. Zuev, P. S.; Sheridan, R. S.; Sauers, R. R.; Moss, R. A.; Chu, G. "Conformational Product Control in the Low-Temperature Photochemistry of Cyclopropylcarbenes," Org. Lett., 2006,  , 4963 - 4966.
26. Roth, H. D.; Herbertz, T.; Sauers, R. R.; Weng, H. "Intramoledcular Nucleophilic Capture of Radical Cations by Tethered Hydroxy Functions," Tetrahedron, 2006, 62, 6471-6489.
27. Kolakowski, R. V.; Shangguan, N.; Wang, Z. Sauers, R. R.; Williams, L. J. "Mechanism of Thio Acid/Azide Amidation," J. Amer. Chem. Soc. 2006, 128, 5695-5702.