R. James Cross

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Name: Jr., R. James Cross

Organization: Yale University , USA

Department: Department of Chemistry

Title: (PhD)

TOPICS

Physical Chemistry

Chemicals
References

Deuterated Ethanol as a Probe for Measuring Equilibrium Isotope Effects for Hydroxyl Exchange

Co-reporter:Hai Xu, Siqi Zhao, Xiang Xiong, Jiayao Yao, R. James Cross, and Martin Saunders

The Journal of Physical Chemistry A March 23, 2017 Volume 121(Issue 11) pp:2288-2288

Publication Date(Web):March 3, 2017

DOI:10.1021/acs.jpca.7b00514

Equilibrium deuterium isotope effects for exchange of hydroxyl deuterons and protons among tert-butanol, phenol, ethanethiol, diethylamine, and ethanol were measured by using NMR and also calculated theoretically. Deuterated ethanol could be used as a probe for measuring equilibrium isotope effects (EIE) for hydroxyl exchange; tert-butanol, phenol, ethanethiol, diethylamine, and pyrrole were used as five representive examples. A procedure called the “one-atom isotope effect” was used to save time in the calculations.

NMR Temperature-Jump Method for Measuring Reaction Rates: Reaction of Dimethylanthracene with H2@C60

Co-reporter:Michael Frunzi, Hai Xu, R. James Cross and Martin Saunders

The Journal of Physical Chemistry A 2009 Volume 113(Issue 17) pp:4996-4999

Publication Date(Web):April 6, 2009

DOI:10.1021/jp901230y

We show a simple variant on Eigen’s familiar temperature-jump method to measure rate constants. The sample is prepared in a sealed NMR tube, which is heated and then abruptly cooled. The NMR spectrum is then taken repeatedly until equilibrium is reestablished at the new temperature. The sample can be used over and over again. We demonstrate the technique on the reversible addition of 9,10-dimethylantracene to C60. The C60 contains H2, and this provides an NMR signal upfield from TMS, well away from the rest of the spectrum. We show that the equilibrium constant for H2@C60 is the same as that for 3He@C60.

Vibration−Rotation Spectroscopy of Molecules Trapped inside C60

Co-reporter:R. James Cross

The Journal of Physical Chemistry A 2008 Volume 112(Issue 31) pp:7152-7156

Publication Date(Web):July 4, 2008

DOI:10.1021/jp802544p

A simple model is developed to treat the energy levels and spectroscopy of diatomic molecules inside C60. The C60 cage is treated as spherically symmetric, and the coupling to the C60 vibrations is ignored. The remaining six degrees of freedom correspond to the vibrations and rotations of the diatomic molecule and the rattling vibration of the molecule inside the cage. By using conservation of angular momentum, we can remove two of these motions and simplify the calculations. The resulting energy levels are simple and can be labeled by a set of quantum numbers. The IR and Raman spectra look like those of gas-phase diatomic molecules at low temperatures. At higher temperatures, hot bands due to the low-frequency rattling mode appear, and the spectrum becomes congested, looking like a solution spectrum.

Kinetic Energy Release of C70+ and Its Endohedral Cation N@C70+: Activation Energy for N Extrusion

Co-reporter:Baopeng Cao Dr.;Tikva Peres;Chava Lifshitz Dr. Dr.;Martin Saunders Dr.

Chemistry - A European Journal 2006 Volume 12(Issue 8) pp:

Publication Date(Web):13 JAN 2006

DOI:10.1002/chem.200501119

Unimolecular decomposition of C₇₀⁺ and its endohedral cation N@C₇₀⁺ were studied by high-resolution mass-analyzed ion kinetic energy (MIKE) spectrometry. Information on the energetics and dynamics of these reactions was extracted. C₇₀⁺ dissociates unimolecularly by loss of a C₂ unit, whereas N@C₇₀⁺ expels the endohedral N atom. Kinetic energy release distributions (KERDs) in these reactions were measured. By use of finite heat bath theory (FHBT), the binding energy for C₂ emission from C₇₀⁺ and the activation energy for N elimination from N@C₇₀⁺ were deduced from KERDs in the light of a recent finding that fragmentation of fullerene cations proceeds via a very loose transition state. The activation energy measured for N extrusion from N@C₇₀⁺ was found to be lower than that for C₂ evaporation, higher than the value from its neutral molecule N@C₇₀ obtained on the basis of thermal stability measurements, and coincident with the theoretical value. The results provide confirmation that the proposed extrusion mechanism in which the N atom escapes from the cage via formation of an aza-bridged intermediate is correct.

Titelbild

Co-reporter:Yves Rubin ;Thibaut Jarrosson;Guan-Wu Wang Dr.;Michael D. Bartberger Dr.;K. N. Houk ;Georg Schick Dr.;Martin Saunders

Angewandte Chemie 2001 Volume 113(Issue 8) pp:

Publication Date(Web):17 APR 2001

DOI:10.1002/1521-3757(20010417)113:8<1361::AID-ANGE1361>3.0.CO;2-C

Das Titelbild zeigt den Vorgang der Wasserstoff- und Heliuminsertion/abgabe, der erstmals mit einem offenen Fullerenderivat (im Hintergrund angedeutet) gelang. Die experimentelle Aktivierungsbarriere für die Heliumdekomplexierung konnte bestimmt werden; sie ist sehr gut mit dem berechneten Wert (Dichtefunktionaltheorie) in Einklang. Die Barriere für die Komplexierung/Dekomplexierung von H₂ ist interessanterweise fast doppelt so groß wie die bei Helium, wie das Energiediagramm im Vordergrund illustriert. Der Grund für den Unterschied ist die größere, gestreckte Oberfläche von H₂, das stärkere van-der-Waals-Wechselwirkungen im Übergangszustand eingeht als Helium, obwohl beide Atome denselben Radius haben. Mehr über diesen Prozess erfahren Sie in dem Beitrag von Rubin, Houk, Saunders, Cross et al. auf S. 1591 ff.

CAS:957761-33-0

Pentacyclo[19.3.1.13,7.19,13.115,19]octacosa-1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23-dodecaene-5,11,17,23-tetracarboxylic acid, 25,26,27,28-tetrakis(phenylmethoxy)-

CAS:903905-60-2

Pentacyclo[19.3.1.13,7.19,13.115,19]octacosa-1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23-dodecaene-5,11,17,23-tetracarboxylic acid, 25,26,27,28-tetrakis(phenylmethoxy)-

Acetic acid, 2-azido-, 2,5-dioxo-1-pyrrolidinyl ester

CAS:824426-32-6

Acetic acid, 2-azido-, 2,5-dioxo-1-pyrrolidinyl ester

L-Alanine, 3-azido-N-[(9H-fluoren-9-ylmethoxy)carbonyl]-

CAS:684270-46-0

L-Alanine, 3-azido-N-[(9H-fluoren-9-ylmethoxy)carbonyl]-

BENZOIC ACID, 4-IODO-3-(1-METHYLETHOXY)-, METHYL ESTER

CAS:681465-87-2

BENZOIC ACID, 4-IODO-3-(1-METHYLETHOXY)-, METHYL ESTER

2-PYRIDINECARBOXYLIC ACID, 5-[[[5-[[[5-AMINO-6-[2-(1,1-DIMETHYLETHOXY)-2-OXOETHOXY]-2-PYRIDINYL]CARBONYL]AMINO]-6-[2-(1,1-DIMETHYLETHOXY)-2-OXOETHOXY]-2-PYRIDINYL]CARBONYL]AMINO]-6-[2-(1,1-DIMETHYLETHOXY)-2-OXOETHOXY]-, METHYL ESTER

CAS:653574-48-2

2-PYRIDINECARBOXYLIC ACID, 5-[[[5-[[[5-AMINO-6-[2-(1,1-DIMETHYLETHOXY)-2-OXOETHOXY]-2-PYRIDINYL]CARBONYL]AMINO]-6-[2-(1,1-DIMETHYLETHOXY)-2-OXOETHOXY]-2-PYRIDINYL]CARBONYL]AMINO]-6-[2-(1,1-DIMETHYLETHOXY)-2-OXOETHOXY]-, METHYL ESTER

2-PYRIDINECARBOXYLIC ACID, 6-[2-(1,1-DIMETHYLETHOXY)-2-OXOETHOXY]-5-[[[6-[2-(1,1-DIMETHYLETHOXY)-2-OXOETHOXY]-5-[[[6-[2-(1,1-DIMETHYLETHOXY)-2-OXOETHOXY]-5-NITRO-2-PYRIDINYL]CARBONYL]AMINO]-2-PYRIDINYL]CARBONYL]AMINO]-, METHYL ESTER

CAS:653574-47-1

2-PYRIDINECARBOXYLIC ACID, 6-[2-(1,1-DIMETHYLETHOXY)-2-OXOETHOXY]-5-[[[6-[2-(1,1-DIMETHYLETHOXY)-2-OXOETHOXY]-5-[[[6-[2-(1,1-DIMETHYLETHOXY)-2-OXOETHOXY]-5-NITRO-2-PYRIDINYL]CARBONYL]AMINO]-2-PYRIDINYL]CARBONYL]AMINO]-, METHYL ESTER

2-Pyridinecarboxylic acid,5-amino-6-[2-(1,1-dimethylethoxy)-2-oxoethoxy]-, methyl ester

CAS:653574-41-5

2-Pyridinecarboxylic acid,5-amino-6-[2-(1,1-dimethylethoxy)-2-oxoethoxy]-, methyl ester

2-PYRIDINECARBOXYLIC ACID, 6-[2-(1,1-DIMETHYLETHOXY)-2-OXOETHOXY]-5-NITRO-, METHYL ESTER

CAS:653574-39-1

2-PYRIDINECARBOXYLIC ACID, 6-[2-(1,1-DIMETHYLETHOXY)-2-OXOETHOXY]-5-NITRO-, METHYL ESTER

2-PYRIDINECARBOXYLIC ACID, 6-(CARBOXYMETHOXY)-5-[[[6-(CARBOXYMETHOXY)-5-[[[6-(CARBOXYMETHOXY)-5-NITRO-2-PYRIDINYL]CARBONYL]AMINO]-2-PYRIDINYL]CARBONYL]AMINO]-, 2-METHYL ESTER

CAS:653574-36-8

2-PYRIDINECARBOXYLIC ACID, 6-(CARBOXYMETHOXY)-5-[[[6-(CARBOXYMETHOXY)-5-[[[6-(CARBOXYMETHOXY)-5-NITRO-2-PYRIDINYL]CARBONYL]AMINO]-2-PYRIDINYL]CARBONYL]AMINO]-, 2-METHYL ESTER