13C NMR studies of hydrocarbon guests in synthetic structure H gas hydrates: Experiment and computation

Jong Won Lee, Hailong Lu, Igor L. Moudrakovski, Christopher I. Ratcliffe, Ryo Ohmura, Saman Alavi, John A. Ripmeester

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

13C NMR chemical shifts were measured for pure (neat) liquids and synthetic binary hydrate samples (with methane help gas) for 2-methylbutane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylpentane, 3-methylpentane, methylcyclopentane, and methylcyclohexane and ternary structure H (sH) clathrate hydrates of n-pentane and n-hexane with methane and 2,2-dimethylbutane, all of which form sH hydrates. The 13C chemical shifts of the guest atoms in the hydrate are different from those in the free form, with some carbon atoms shifting specifically upfield. Such changes can be attributed to conformational changes upon fitting the large guest molecules in hydrate cages and/or interactions between the guests and the water molecules of the hydrate cages. In addition, powder X-ray diffraction measurements revealed that for the hexagonal unit cell, the lattice parameter along the a-axis changes with guest hydrate former molecule size and shape (in the range of 0.1 Å) but a much smaller change in the c-axis (in the range of 0.01 Å) is observed. The 13C NMR chemical shifts for the pure hydrocarbons and all conformers were calculated using the gauge invariant atomic orbital method at the MP2/6-311+G(2d,p) level of theory to quantify the variation of the chemical shifts with the dihedral angles of the guest molecules. Calculated and measured chemical shifts are compared to determine the relative contribution of changes in the conformation and guest-water interactions to the change in chemical shift of the guest upon clathrate hydrate formation. Understanding factors that affect experimental chemical shifts for the enclathrated hydrocarbons will help in assigning spectra for complex hydrates recovered from natural sites.

Original languageEnglish
Pages (from-to)1650-1657
Number of pages8
JournalJournal of Physical Chemistry A
Volume115
Issue number9
DOIs
Publication statusPublished - 2011 Mar 10

Fingerprint

Gas hydrates
Hydrocarbons
Hydrates
hydrates
Chemical shift
hydrocarbons
Nuclear magnetic resonance
chemical equilibrium
nuclear magnetic resonance
gases
Experiments
Molecules
clathrates
Methane
molecules
methane
Atoms
Water
pentanes
Dihedral angle

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Lee, J. W., Lu, H., Moudrakovski, I. L., Ratcliffe, C. I., Ohmura, R., Alavi, S., & Ripmeester, J. A. (2011). 13C NMR studies of hydrocarbon guests in synthetic structure H gas hydrates: Experiment and computation. Journal of Physical Chemistry A, 115(9), 1650-1657. https://doi.org/10.1021/jp1118184

13C NMR studies of hydrocarbon guests in synthetic structure H gas hydrates : Experiment and computation. / Lee, Jong Won; Lu, Hailong; Moudrakovski, Igor L.; Ratcliffe, Christopher I.; Ohmura, Ryo; Alavi, Saman; Ripmeester, John A.

In: Journal of Physical Chemistry A, Vol. 115, No. 9, 10.03.2011, p. 1650-1657.

Research output: Contribution to journalArticle

Lee, JW, Lu, H, Moudrakovski, IL, Ratcliffe, CI, Ohmura, R, Alavi, S & Ripmeester, JA 2011, '13C NMR studies of hydrocarbon guests in synthetic structure H gas hydrates: Experiment and computation', Journal of Physical Chemistry A, vol. 115, no. 9, pp. 1650-1657. https://doi.org/10.1021/jp1118184
Lee, Jong Won ; Lu, Hailong ; Moudrakovski, Igor L. ; Ratcliffe, Christopher I. ; Ohmura, Ryo ; Alavi, Saman ; Ripmeester, John A. / 13C NMR studies of hydrocarbon guests in synthetic structure H gas hydrates : Experiment and computation. In: Journal of Physical Chemistry A. 2011 ; Vol. 115, No. 9. pp. 1650-1657.
@article{6f7c5ee2a7724aaaaea24e311abd01d6,
title = "13C NMR studies of hydrocarbon guests in synthetic structure H gas hydrates: Experiment and computation",
abstract = "13C NMR chemical shifts were measured for pure (neat) liquids and synthetic binary hydrate samples (with methane help gas) for 2-methylbutane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylpentane, 3-methylpentane, methylcyclopentane, and methylcyclohexane and ternary structure H (sH) clathrate hydrates of n-pentane and n-hexane with methane and 2,2-dimethylbutane, all of which form sH hydrates. The 13C chemical shifts of the guest atoms in the hydrate are different from those in the free form, with some carbon atoms shifting specifically upfield. Such changes can be attributed to conformational changes upon fitting the large guest molecules in hydrate cages and/or interactions between the guests and the water molecules of the hydrate cages. In addition, powder X-ray diffraction measurements revealed that for the hexagonal unit cell, the lattice parameter along the a-axis changes with guest hydrate former molecule size and shape (in the range of 0.1 {\AA}) but a much smaller change in the c-axis (in the range of 0.01 {\AA}) is observed. The 13C NMR chemical shifts for the pure hydrocarbons and all conformers were calculated using the gauge invariant atomic orbital method at the MP2/6-311+G(2d,p) level of theory to quantify the variation of the chemical shifts with the dihedral angles of the guest molecules. Calculated and measured chemical shifts are compared to determine the relative contribution of changes in the conformation and guest-water interactions to the change in chemical shift of the guest upon clathrate hydrate formation. Understanding factors that affect experimental chemical shifts for the enclathrated hydrocarbons will help in assigning spectra for complex hydrates recovered from natural sites.",
author = "Lee, {Jong Won} and Hailong Lu and Moudrakovski, {Igor L.} and Ratcliffe, {Christopher I.} and Ryo Ohmura and Saman Alavi and Ripmeester, {John A.}",
year = "2011",
month = "3",
day = "10",
doi = "10.1021/jp1118184",
language = "English",
volume = "115",
pages = "1650--1657",
journal = "Journal of Physical Chemistry A",
issn = "1089-5639",
publisher = "American Chemical Society",
number = "9",

}

TY - JOUR

T1 - 13C NMR studies of hydrocarbon guests in synthetic structure H gas hydrates

T2 - Experiment and computation

AU - Lee, Jong Won

AU - Lu, Hailong

AU - Moudrakovski, Igor L.

AU - Ratcliffe, Christopher I.

AU - Ohmura, Ryo

AU - Alavi, Saman

AU - Ripmeester, John A.

PY - 2011/3/10

Y1 - 2011/3/10

N2 - 13C NMR chemical shifts were measured for pure (neat) liquids and synthetic binary hydrate samples (with methane help gas) for 2-methylbutane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylpentane, 3-methylpentane, methylcyclopentane, and methylcyclohexane and ternary structure H (sH) clathrate hydrates of n-pentane and n-hexane with methane and 2,2-dimethylbutane, all of which form sH hydrates. The 13C chemical shifts of the guest atoms in the hydrate are different from those in the free form, with some carbon atoms shifting specifically upfield. Such changes can be attributed to conformational changes upon fitting the large guest molecules in hydrate cages and/or interactions between the guests and the water molecules of the hydrate cages. In addition, powder X-ray diffraction measurements revealed that for the hexagonal unit cell, the lattice parameter along the a-axis changes with guest hydrate former molecule size and shape (in the range of 0.1 Å) but a much smaller change in the c-axis (in the range of 0.01 Å) is observed. The 13C NMR chemical shifts for the pure hydrocarbons and all conformers were calculated using the gauge invariant atomic orbital method at the MP2/6-311+G(2d,p) level of theory to quantify the variation of the chemical shifts with the dihedral angles of the guest molecules. Calculated and measured chemical shifts are compared to determine the relative contribution of changes in the conformation and guest-water interactions to the change in chemical shift of the guest upon clathrate hydrate formation. Understanding factors that affect experimental chemical shifts for the enclathrated hydrocarbons will help in assigning spectra for complex hydrates recovered from natural sites.

AB - 13C NMR chemical shifts were measured for pure (neat) liquids and synthetic binary hydrate samples (with methane help gas) for 2-methylbutane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylpentane, 3-methylpentane, methylcyclopentane, and methylcyclohexane and ternary structure H (sH) clathrate hydrates of n-pentane and n-hexane with methane and 2,2-dimethylbutane, all of which form sH hydrates. The 13C chemical shifts of the guest atoms in the hydrate are different from those in the free form, with some carbon atoms shifting specifically upfield. Such changes can be attributed to conformational changes upon fitting the large guest molecules in hydrate cages and/or interactions between the guests and the water molecules of the hydrate cages. In addition, powder X-ray diffraction measurements revealed that for the hexagonal unit cell, the lattice parameter along the a-axis changes with guest hydrate former molecule size and shape (in the range of 0.1 Å) but a much smaller change in the c-axis (in the range of 0.01 Å) is observed. The 13C NMR chemical shifts for the pure hydrocarbons and all conformers were calculated using the gauge invariant atomic orbital method at the MP2/6-311+G(2d,p) level of theory to quantify the variation of the chemical shifts with the dihedral angles of the guest molecules. Calculated and measured chemical shifts are compared to determine the relative contribution of changes in the conformation and guest-water interactions to the change in chemical shift of the guest upon clathrate hydrate formation. Understanding factors that affect experimental chemical shifts for the enclathrated hydrocarbons will help in assigning spectra for complex hydrates recovered from natural sites.

UR - http://www.scopus.com/inward/record.url?scp=79952275303&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=79952275303&partnerID=8YFLogxK

U2 - 10.1021/jp1118184

DO - 10.1021/jp1118184

M3 - Article

C2 - 21329330

AN - SCOPUS:79952275303

VL - 115

SP - 1650

EP - 1657

JO - Journal of Physical Chemistry A

JF - Journal of Physical Chemistry A

SN - 1089-5639

IS - 9

ER -