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A Research Paper On
Molecular Modeling Of Phosphine(𝑷𝑯𝟑 ), Water(𝑯𝟐 𝑶) And Dimer
Between Both
By:-Your Name
Department:University:-
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Introduction
Phosphine(𝑷𝑯𝟑 ):
Phosphine is also known as hydrogen phosphide, phosphorus hydride or phosphorus trihydride.It
is a low molecular weight, low boiling point compound that diffuses rapidly and penetrates
deeply into materials, such as large bulks of grain or tightly packed materials. Phosphine is very
toxic to all forms of animal life, hence exposure of human beings even to small amounts should
be avoided. Poisoning can result from ingestion or inhalation; however, the gas is not absorbed
through the skin. Phosphine is a by-product generated during the synthesis of hydriodic acid
from iodine and red phosphorus. It is produced when red phosphorus contacts caustics and/or
acids, especially in the presence of a metal. A number of cooks in clandestine methamphetamine
drug labs have died because of inadvertent exposure to phosphine. Phosphine is a colorless gas at
room temperature. Phosphine is often reported as having a disagreeable, garlic-like odor; like the
odor of decaying fish. Pure phosphine is odorless at concentrations up to 200 ppm, a highly toxic
level. The characteristic garlic-like odor often attributed to phosphine is actually due to the
presence of impurities. The vapor density of phosphine is 1.2 (air = 1); therefore, phosphine is
slightly heavier than air. Phosphine reacts with many metals, including copper, silver, gold, and
the salts of these metals. In molecular geometry of 𝑷𝑯𝟑 all the three P-H bonds are of equal
length. The atomic masses of phosphorous and hydrogen are 31 and 1 respectively hence
molecular weight of phosphine is 34. Phosphine may react spontaneously and violently on
contact with air at room temperature. Phosphine also reacts violently with oxygen, oxidizers
(e.g., nitric acid and nitrogen oxides), metal nitrates, halogens (fluorine, chlorine, bromine and
iodine), and many other substances creating a fire and explosion hazard.
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Water(𝑯𝟐 𝑶):
water, odorless, tasteless, transparent liquid that is colorless in small amounts but exhibits a
bluish tinge in large quantities. It is the most familiar and abundant liquid on earth. Chemically,
water is a compound of hydrogen and oxygen, having the formula H2O. It is chemically active,
reacting with certain metals and metal oxides to form bases, and with certain oxides of nonmetals
to form acids. It reacts with certain organic compounds to form a variety of products, e.g.,
alcohols from alkenes. Because water is a polar compound, it is a good solvent. Although
completely pure water is a poor conductor of electricity, it is a much better conductor than most
other pure liquids because of its self-ionization, i.e., the ability of two water molecules to react to
form a hydroxide ion, OH - , and a hydronium ion, H3O+. Its polarity and ionization are both
due to the high dielectric constant of water.Water has interesting thermal properties. When
heated from 0°C, its melting point, to 4°C, it contracts and becomes more dense; most other
substances expand and become less dense when heated. Conversely, when water is cooled in this
temperature range, it expands. It expands greatly as it freezes; as a consequence, ice is less dense
than water and floats on it. Because of hydrogen bonding between water molecules, the latent
heats of fusion and of evaporation and the heat capacity of water are all unusually high. For these
reasons, water serves both as a heat-transfer medium (e.g., ice for cooling and steam for heating)
and as a temperature regulator (the water in lakes and oceans helps regulate the climate). Many
of the physical and chemical properties of water are due to its structure. The atoms in the water
molecule are arranged with the two HO bonds at an angle of about 105° rather than on directly
opposite sides of the oxygen atom. The asymmetrical shape of the molecule arises from a
tendency of the four electron pairs in the valence shell of oxygen to arrange themselves
symmetrically at the vertices of a tetrahedron around the oxygen nucleus. The two pairs
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associated with covalent bonds (see chemical bond) holding the hydrogen atoms are drawn
together slightly, resulting in the angle of 105° between these bonds. This arrangement results in
a polar molecule, since there is a net negative charge toward the oxygen end (the apex) of the Vshaped molecule and a net positive charge at the hydrogen end. The electric dipole gives rise to
attractions between neighboring opposite ends of water molecules, with each oxygen being able
to attract two nearby hydrogen atoms of two other water molecules. Such hydrogen bonding, as
it is called, has also been observed in other hydrogen compounds. Although considerably weaker
than the covalent bonds holding the water molecule together, hydrogen bonding is strong enough
to keep water liquid at ordinary temperatures; its low molecular weight would normally tend to
make it a gas at such temperatures.Various other properties of water, such as its high specific
heat, are due to these hydrogen bonds. As the temperature of water is lowered, clusters of
molecules form through hydrogen bonding, with each molecule being linked to others by up to
four hydrogen bonds, each oxygen atom tending to surround itself with four hydrogen atoms in a
tetrahedral arrangement. Hexagonal rings of oxygen atoms are formed in this way, with alternate
atoms in either a higher or lower plane than their neighbors to create a kinked three-dimensional
structure.
Dimer of Phosphine(𝑷𝑯𝟑 ) and Water(𝑯𝟐 𝑶):
The dimer formed between phosphine and water is due to presence of hydrogen in these
molecules. Since hydrogen is present weakly connected hydrogen bonds are formed between
these molecules. Phosphine doesn’t dissolve in water also if dissolves, dissolution is very
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slightly.
Fig 1.1 Structure of dimer of phosphine and water.
Methodology:
I have used Avogadro and Gemess to find various parameters for molecules in our consideration.
1) For Phosphine(𝑷𝑯𝟑 )
Open Avogadro software switch to build mode and draw the molecular structure for
Phosphine.
The molecular optimization is performed under Equilibrium geometry for all the
molecules in our consideration.
To perform calculations goto extensions -> Gamess -> Inputgenerator
Select optimization method as equilibrium geometry.
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Fig 1.2:- Molecular structure of Phosphine.
2) Water(𝑯𝟐 𝑶)
Fig 1.3:- Molecular structure of water.
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3) Dimer of phosphine and water
Result:
Various parameters as observed are following:1) Phosphine
S.no.
Quantity
Set1
Set2
Set3
1.
Optimized Energy(kj/mol)
180.753
180.762
180.754
2.
Dipole Moment(D)
0.58
0.59
0.57
3.
Bond Angle(H-P-H)(Degree)
93.48
93.42
93.46
4.
Bond Length(Armstrong)
1.4140
1.4287
1.4167
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5.
Enthalpy(kj/mol)
210
210.01
210
6.
Gibb’s Free Energy(kj/mol)
13.400
13.410
13.401
S.no.
Quantity
Set1
Set2
Set3
1.
Optimized Energy(kj/mol)
5.83295e-13
5.83297e-13
5.83299e-13
2.
Dipole Moment(D)
1.85
1.87
1.84
3.
Bond Angle(H-P-H)(Degree)
104.36
103.94
104.18
4.
Bond Length(Armstrong)
0.9588
0.9665
0.9616
5.
Enthalpy(kj/mol)
410
410.20
409.89
6.
Gibb’s Free Energy(kj/mol)
-237.14
-237.10
-237.11
2) Water
3) Dimer of Water and phosphine
S. no.
Quantity
Set1
Set2
Set3
1.
Intermolecular
3.6238
3.5999
3.5972
distance(Armstrong)
2.
Dipole Moment(D)
2.638
2.635
2.637
3.
Optimized
183.447
183.456
183.449
energy(kj/mol)
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References:
1. K. Morokuma and C. Muguruma, J. Am. Chem. Soc. 116, 10316 1994
2. V. Vaida and J. E. Headrick, J. Phys. Chem. A 104, 5401 2000.
3 V. Vaida, H. G. Kjaergaard, and K. J. Feierabend, Int. Rev. Phys. Chem.22, 203(2003)
4. www.avogadro.openmolecules.net