4th EucheMs chemistry congress

tuesday, 28-Aug 2012
s818
chem. Listy 106, s587–s1425 (2012)
Physical, theoretical and Computational Chemistry
theoretical Chemisry – iii
o - 2 4 2
An ir And dft Study of AMMoniA interACtion
with foSSiL PAttern in KBr MAtrix
i. vorotyntSev 1 , i. GreenvALd 2 , i. KALAGAev 2 ,
e. SutyAGinA 2 , A. PetuKhov 1 , n. PetuKhovA 1
1 Nizhny Novgorod State Technical University n.a. R.Y. Alekseev,
PTMCET department, Nizhny Novgorod, Russia
2 Nizhny Novgorod State Technical University n.a. R.Y. Alekseev,
OCSM department, Nizhny Novgorod, Russia
The role of ammonia in biological processes is not quite
clear yet. Nevertheless in the last years the interest to the
interaction of ammonia and fossil patterns is becoming immense.
The problem of ammonia action in nature is connected in the first
regard with the possibility of complex formation as an initial step
in molecular transformation.The presented work the mechanism
of appearance and structure of ammonia intermediates with water,
cellulose acetate and betuline, employing IR experimental and
DFT theoretical approaches is presenting.Usually the unstable
adducts are fixed in the low temperature films. We have suggested
a new variant of spectral method, using the stabilization of
intermediates in KBr-matrix. The mentioned experimental tactic
permits to investigate the complexes and their conversion at
normal conditions. In this way we have revealed in IR-spectra of
KBr-pallets, saturated by ammonia/water mixture before the
pressing,in 3600-3000cm-1and 1600-1400cm-1region the new
bands, which can be assigned to the water intermediates and
ammonium cation vibrations. The experiments have shown that
both weak water complexes and hydroxonium adducts can be
stabilized in KBr-matrix. These data can be considered to some
extent as the evidence of hydrogen transfer from water to
ammonia molecule. At the interaction of cellulose acetate and
ammonia it was established the existance of ammonia adducts
with cellulose pattern in KBr-matrix. However for this system the
hydrogen transfer between coupled molecules is not observed. In
the case of betuline/ammonia system the IR-study indicates the
hydrogen transfer in the intermediates of both betuline and
ammonia.
The conducted DFT-calculations in terms of GAUSSIAN
procedure have manifested the complex formation in the
presented systems. We have considered different species of
intermediates, including the varied ratio of components.The
calculated frequencies agree well with the experimental values in
general.
Acknowledgments: This work has been financially supported by
Russia Foundation of Basic Research (11-08-00707)
Keywords: ammonia; cellulose acetate; betuline; hydrogen
bones; IR-spectroscopy;
theoretical Chemisry – iii
4 th EucheMs chemistry congress
o - 2 4 3
CAr-PArrineLLo MoLeCuLAr dynAMiCS
SiMuLAtionS with GriMMe vdw CorreCtion
for CLAthrAte hydrAteS ConSiStinG of
ALCohoL And fLuoroCArBon MoLeCuLeS
M. hirAtSuKA 1 , r. ohMurA 1 , S. AMAdeu K. 2 ,
K. yASuoKA 1
1 Keio University, Department of Mechanical Engineering,
Yokohama, Japan
2 Colorado School of Mines, Center for Hydrate Research
Department of Chemical & Biological Engineering, Golden,
USA
Clathrate hydrates are crystalline compounds consisting of
hydrogen-bonded water molecules forming cages that enclose
guest molecules. Clathrate hydrates are expected to be used in
transport of natural gas, storage of unstable molecules, and future
energy resource. Since the phase equilibrium conditions of the
clathrate hydrates are significant for these applications, variety of
experimental measurements and theoretical studies have been
performed to understand the stability of the hydrate phases.
Although many guest substances are known to form hydrates,
alcohol and fluorocarbon molecules are most important ones.
Recently, several alcohol and halogenated hydrocarbon molecules
such as ethanol, butanol, fluorocarbons are reported as promoters
for hydrate formation. However, in the previous understanding,
the guest molecules that have large dipole moment and coulomb
interactions between cage water molecules like methanol are
known as inhibitor for hydrate. Therefore the mechanisms of the
stabilizations of hydrate phase by the alcohol and halogenated
hydrocarbon molecules that have large dipole moments are still
missing. Furtherer understanding of the effect for phase
equilibrium conditions from the interactions between the guest
and cage water molecules is important for future applications of
clathrate hydrates.
The ab initio molecular dynamics simulation is a suitable
way to observe the molecular behavior of the guest molecules in
the hydrates. We performed Car-Parrinello MD simulation with
vdW correction based on the Grimme model for the alcohol
hydrates and fluorocarbon hydrates to calculate molecular
motions of guest in the cages. As result, the hydrogen-bonding
between guest and water molecules were observed and the
vibrational spectrum was changed for alcohol hydrate. The
differences of the molecular motions of fluorocarbons were also
reported. The CH2F2 and CHF3 molecule moved along the long
axis in the 51262 cages.
Keywords: Inclusion compounds; Molecular dynamics; Ab
initio calculations; Vibrational spectroscopy;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc