1
|
Pathak B, Kesari S, Patwari GN. Enticing a Proton using Single Ammonia Molecule as Bait. J Phys Chem B 2024; 128:1022-1028. [PMID: 38240575 DOI: 10.1021/acs.jpcb.3c06761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2024]
Abstract
In microhydrated acid-solvent clusters, deprotonation of an acid is assisted by a critical number of solvent molecules and a solvent electric field. Born-Oppenheimer molecular dynamics simulations reveal that trifluoroacetic acid undergoes spontaneous proton transfer in water clusters, with the critical number being five. Acetic acid and phenol, on the other hand, do not dissociate even in the presence of a large number of water molecules (in excess of 40). The addition of a single ammonia molecule to the water cluster, which interacts directly with the protic group, lowers the critical number of solvent water molecules required for proton transfer to three and seven in the case of acetic acid and phenol, respectively. The population of the undissociated and the proton-transferred structures get dispersed to form separate islands on the electric field versus the O-H distance representation with the cusp representing the critical values. The critical electric fields for the spontaneous proton transfer are around 254, 237, and 318 MV cm-1 for trifluoroacetic acid, acetic acid, and phenol, respectively. In the case of phenol, the free energy profiles suggest that proton transfer to the ammonia moiety embedded in water promotes proton transfer efficiently due to the higher basicity of ammonia and enhanced hydrogen bonding network of solvent water, vis-à-vis phenol-ammonia clusters.
Collapse
Affiliation(s)
- Bijaya Pathak
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Shaivi Kesari
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - G Naresh Patwari
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| |
Collapse
|
2
|
Meng X, Li X, Zhang Q, Wu L, Cao F. Temperature-dependent structure of 3.5 wt.% NaCl aqueous solution: Theoretical and Raman investigation. J Mol Struct 2022. [DOI: 10.1016/j.molstruc.2021.132279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
|
3
|
Boda M, Patwari GN. Vibrational Stark fields in carboxylic acid dimers. Phys Chem Chem Phys 2022; 24:5879-5885. [PMID: 35195127 DOI: 10.1039/d1cp02211c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Carboxylic acids form exceptionally stable dimers and have been used to model proton and double proton transfer processes. The stabilization energies of the carboxylic acid dimers are very weakly dependent on the nature of substitution. However, the electric field experienced by the OH group of a particular carboxylic acid is dependent more on the nature of the substitution on the dimer partner. In general, the electric field was higher when the partner was substituted with an electron-donating group and lower with an electron-withdrawing substituent on the partner. The Stark tuning rate (Δ) of the O-H stretching vibrations calculated at the MP2/aug-cc-pVDZ level was found to be weakly dependent on the nature of substitution on the carboxylic acid. The average Stark tuning rate of O-H stretching vibrations of a particular carboxylic acid when paired with other acids was 5.7 cm-1 (MV cm-1)-1, while the corresponding average Stark tuning rate of the partner acids due to a particular carboxylic acid was 21.9 cm-1 (MV cm-1)-1. The difference in the Stark tuning rate is attributed to the primary and secondary effects of substitution on the carboxylic acid. The average Stark tuning rate for the anharmonic O-D frequency shifts is about 40-50% higher than the corresponding harmonic O-D frequency shifts calculated at the B3LYP/aug-cc-pVDZ level, much greater than the typical scaling factors used, indicating the strong anharmonicity of O-H/O-D oscillators in carboxylic acid dimers. Finally, the linear correlation observed between pKa and the electric field was used to estimate the pKa of fluoroformic acid to be around 0.9.
Collapse
Affiliation(s)
- Manjusha Boda
- Department of Chemistry, Indian Institute of Technology Bombay, Powai Mumbai 400076, India.
| | - G Naresh Patwari
- Department of Chemistry, Indian Institute of Technology Bombay, Powai Mumbai 400076, India.
| |
Collapse
|
4
|
Singh RK, Pant R, Patwari GN. Ultrafast Proton-Transfer Reaction in Phenol–(Ammonia)n Clusters: An Ab Initio Molecular Dynamics Investigation. J Phys Chem B 2022; 126:1590-1597. [DOI: 10.1021/acs.jpcb.1c09700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Reman Kumar Singh
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Rakesh Pant
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - G. Naresh Patwari
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| |
Collapse
|
5
|
Sadhukhan D, Hsu PJ, Kuo JL, Patwari GN. Is Dissociation of HCl in DMSO Clusters Bistable? J Phys Chem A 2021; 125:10351-10358. [PMID: 34821498 DOI: 10.1021/acs.jpca.1c08627] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dissociation of HCl embedded in dimethyl sulfoxide (DMSO) clusters was investigated by projecting the solvent electric field along the HCl bond using B3LYP-D3/6-31+G(d) and MP2/6-31+G(d,p) levels of theory. A large number of distinct structures (about 1500) consisting of up to five DMSO molecules were considered in the present work for statistical reliability. The B3LYP-D3 calculations reveal that the dissociation of HCl embedded in DMSO clusters requires a critical electric field of 138 MV cm-1 along the H-Cl bond. However, a large number of exceptions wherein the electric field values much higher than the critical electric field of 138 MV cm-1 did not result in dissociation of HCl were observed, in addition to several cases wherein the HCl dissociates with an electric field less than the critical electric field. On the other hand, the MP2 level calculations reveal that the critical electric field for HCl dissociation is about 181 MV cm-1 with almost no exceptions. A comparison of calculations carried out using the MP2 and the B3LYP-D3 levels suggests that the dissociation of HCl embedded in DMSO clusters is bistable at the B3LYP-D3 level, which is an artifact, suggesting that care must be exercised in interpreting the processes of proton transfer. The answer to the question raised as the title of this paper is NO.
Collapse
Affiliation(s)
- Debopriya Sadhukhan
- IITB-Monash Research Academy, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Po-Jen Hsu
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Jer-Lai Kuo
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - G Naresh Patwari
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| |
Collapse
|
6
|
Tohidi Nafe Z, Arshadi N. Theoretical study of the effect of water clusters on the enol content of acetone as a model for understanding the effect of water on enolization reaction. Struct Chem 2021. [DOI: 10.1007/s11224-021-01813-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
7
|
Boda M, Patwari GN. Internal electric fields in methanol [MeOH] 2-6 clusters. Phys Chem Chem Phys 2020; 22:10917-10923. [PMID: 32373804 DOI: 10.1039/c9cp04571f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Water and methanol are well known solvents showing cooperative hydrogen bonding, however the differences in the hydrogen bonding pattern in water and methanol are due to the presence of the methyl group in methanol. The presence of the methyl group leads to formation of C-HO hydrogen bonds apart from the usual O-HO hydrogen bonds. The electric fields evaluated along the hydrogen bonded donor OH and CH groups reveal that the C-HO hydrogen bonds can significantly influence the structure and energetics (by about 20%) of methanol clusters. A linear Stark effect was observed on the hydrogen bonded OH groups in methanol clusters with a Stark tuning rate of 3.1 cm-1 (MV cm-1)-1 as an average behaviour. Furthermore, the Stark tuning of the OH oscillators in methanol depends on their hydrogen bonding environment wherein molecules with the DAA motif show higher rates than the rest. The present work suggests that the OH group of methanol has higher sensitivity as a vibrational probe relative to the OH group of water.
Collapse
Affiliation(s)
- Manjusha Boda
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
| | | |
Collapse
|
8
|
Sadhukhan D, Hazra A, Patwari GN. Bend-to-Break: Curvilinear Proton Transfer in Phenol-Ammonia Clusters. J Phys Chem A 2020; 124:3101-3108. [PMID: 32227953 DOI: 10.1021/acs.jpca.0c00102] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The electric field experienced by the OH group of phenol embedded in the cluster of ammonia molecules depends on the relative orientation of the ammonia molecules, and a critical field of 236 MV cm-1 is essential for the transfer of a proton from phenol to the surrounding ammonia cluster. However, exceptions to this rule were observed, which indicates that the projection of the solvent electric field over the O-H bond is not a definite descriptor of the proton transfer reaction. Therefore, a critical electric field is necessary, but it is not a sufficient condition for the proton abstraction. This, in combination with an adequate solvation of the acceptor ammonia molecule in a triple donor motif that energetically favors the proton transfer process, constitutes necessary and sufficient conditions for the spontaneous proton abstraction. The proton transfer process in phenol-(ammonia)n clusters is statistically favored to occur away from the plane of the phenyl ring and follows a curvilinear path which includes the O-H bond elongation and out-of-plane movement of the proton. Colloquially, this proton transfer can be referred to as a "bend-to-break" process.
Collapse
Affiliation(s)
- Debopriya Sadhukhan
- IITB-Monash Research Academy, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Anirban Hazra
- Department of Chemistry, Indian Institute of Science Education and Research Pune, Dr. Homi Bhabha Road, Pune 411008, India
| | - G Naresh Patwari
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| |
Collapse
|
9
|
Lombard J, Smith VJ, le Roex T, Haynes DA. Crystallisation of organic salts by sublimation: salt formation from the gas phase. CrystEngComm 2020. [DOI: 10.1039/d0ce01470b] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Co-sublimation of two neutral components yields crystals of salts and co-crystals. Experiments show that during sublimation of salts, proton transfer occurs after molecules enter the gas phase.
Collapse
Affiliation(s)
- Jean Lombard
- Department of Chemistry and Polymer Science
- Stellenbosch University
- Stellenbosch
- Republic of South Africa
| | - Vincent J. Smith
- Department of Chemistry
- Rhodes University
- Grahamstown
- Republic of South Africa
| | - Tanya le Roex
- Department of Chemistry and Polymer Science
- Stellenbosch University
- Stellenbosch
- Republic of South Africa
| | - Delia A. Haynes
- Department of Chemistry and Polymer Science
- Stellenbosch University
- Stellenbosch
- Republic of South Africa
| |
Collapse
|
10
|
Sen S, Patwari GN. Electrostatics and Dispersion in X-H···Y (X = C, N, O; Y = N, O) Hydrogen Bonds and Their Role in X-H Vibrational Frequency Shifts. ACS OMEGA 2018; 3:18518-18527. [PMID: 31458423 PMCID: PMC6644087 DOI: 10.1021/acsomega.8b01802] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 11/19/2018] [Indexed: 06/10/2023]
Abstract
The frequency shifts of donor stretching vibration in X-H···Y (X = C, N, O; Y = N, O) hydrogen-bonded complexes of phenylacetylene, indole, and phenol are linearly correlated with the electrostatic component of the interaction energy. This linear correlation suggests that the electrostatic component, which is the first-order perturbative correction to the stabilization energy, is essentially localized on the X-H group. The linear correlation suggests that the electrostatic tuning rate, which is a measure of the X-H oscillator to undergo shifts upon hydrogen bonding per unit increase in the electrostatic component of the stabilization energy, was found to be in the order of O-H > N-H > C-H. Interestingly, for each of the donor groups, viz., C-H, N-H, and O-H, the vibrational frequency shifts were inversely correlated to the dipole moment of the acceptor separately, which is counterintuitive vis-à-vis the electrostatic component. This implies that extrapolation to zero dipole moment of the acceptor will yield very large shifts in the hydrogen-bonded X-H stretching frequencies. The trends in the variation of the dispersion and exchange-repulsion components and the total interaction energy vis-à-vis frequency shifts of donor stretching vibration are similar for hydrogen-bonded complexes of phenylacetylene, indole, and phenol. Furthermore, it was observed that the vibrational frequency shifts of all of the complexes are linearly correlated with the charge transfer from the filled orbital of the hydrogen acceptor to the vacant antibonding (σ*) orbital of the X-H donor group on the basis of natural bonding orbital calculations.
Collapse
Affiliation(s)
| | - G. Naresh Patwari
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| |
Collapse
|
11
|
Kebede GG, Mitev PD, Briels WJ, Hermansson K. Red-shifting and blue-shifting OH groups on metal oxide surfaces - towards a unified picture. Phys Chem Chem Phys 2018; 20:12678-12687. [PMID: 29697122 DOI: 10.1039/c8cp00741a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We analyse the OH vibrational signatures of 56 structurally unique water molecules and 34 structurally unique hydroxide ions in thin water films on MgO(001) and CaO(001), using DFT-generated anharmonic potential energy surfaces. We find that the OH stretching frequencies of intact water molecules on the surface are always downshifted with respect to the gas-phase species while the OH- groups are either upshifted or downshifted. Despite these differences, the main characteristics of the frequency shifts for all three types of surface OH groups (OHw, OsH and OHf) can be accounted for by one unified expression involving the in situ electric field from the surrounding environment, and the gas-phase molecular properties of the vibrating species (H2O or OH-). The origin behind the different red- and blueshift behaviour can be traced back to the fact that the molecular dipole moment of a gas-phase water molecule increases when an OH bond is stretched, but the opposite is true for the hydroxide ion. We propose that familiarity with the relations presented here will help surface scientists in the interpretation of vibrational OH spectra for thin water films on ionic crystal surfaces.
Collapse
Affiliation(s)
- Getachew G Kebede
- Department of Chemistry-Ångström, Uppsala University, Box 538, Uppsala, SE-75121, Sweden.
| | | | | | | |
Collapse
|
12
|
Tao Z, Wang X, Wei Y, Lv L, Wu D, Yang M. A theoretical study of molecular structure, optical properties and bond activation of energetic compound FOX-7 under intense electric fields. Chem Phys 2017. [DOI: 10.1016/j.chemphys.2016.12.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
13
|
Boda M, Naresh Patwari G. Insights into acid dissociation of HCl and HBr with internal electric fields. Phys Chem Chem Phys 2017; 19:7461-7464. [DOI: 10.1039/c6cp08870h] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A critical electric field exerted by the solvent on the ionizable group leads to acid dissociation.
Collapse
Affiliation(s)
- Manjusha Boda
- Department of Chemistry
- Indian Institute of Technology Bombay
- Mumbai 400076
- India
| | - G. Naresh Patwari
- Department of Chemistry
- Indian Institute of Technology Bombay
- Mumbai 400076
- India
| |
Collapse
|
14
|
Schneider SH, Boxer SG. Vibrational Stark Effects of Carbonyl Probes Applied to Reinterpret IR and Raman Data for Enzyme Inhibitors in Terms of Electric Fields at the Active Site. J Phys Chem B 2016; 120:9672-84. [PMID: 27541577 DOI: 10.1021/acs.jpcb.6b08133] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
IR and Raman frequency shifts have been reported for numerous probes of enzyme transition states, leading to diverse interpretations. In the case of the model enzyme ketosteroid isomerase (KSI), we have argued that IR spectral shifts for a carbonyl probe at the active site can provide a connection between the active site electric field and the activation free energy (Fried et al. Science 2014, 346, 1510-1514). Here we generalize this approach to a much broader set of carbonyl probes (e.g., oxoesters, thioesters, and amides), first establishing the sensitivity of each probe to an electric field using vibrational Stark spectroscopy, vibrational solvatochromism, and MD simulations, and then applying these results to reinterpret data already in the literature for enzymes such as 4-chlorobenzoyl-CoA dehalogenase and serine proteases. These results demonstrate that the vibrational Stark effect provides a general framework for estimating the electrostatic contribution to the catalytic rate and may provide a metric for the design or modification of enzymes. Opportunities and limitations of the approach are also described.
Collapse
Affiliation(s)
- Samuel H Schneider
- Department of Chemistry, Stanford University , Stanford, California 94305-5012, United States
| | - Steven G Boxer
- Department of Chemistry, Stanford University , Stanford, California 94305-5012, United States
| |
Collapse
|