NITROUS OXIDE - DOC

							NITROUS OXIDE: A Serious Study Of
       A Laughing Matter
                        By: Daniel Peters




    Molecular Modeling Using Computational Chemistry Methods
                         Lew Acampora


                          July 13, 2002
In my research, I will examine the history of nitrous oxide as well as its applications

today. I will closely look at its use as an anesthetic for dental and medical patients and as

a propellant for modern racecars. The structure of the gas will also be studied. In

particular, I will look further into the bonding of the individual atoms that make up the

molecule, as well as how the atomic orbitals affect the molecular orbitals and electron

density of nitrous oxide. Finally, I will draw conclusions as to how nitrous oxide is

related to carbon dioxide from an energy standpoint. The results of comparing these two

atoms are particularly interesting because they are isoelectronic molecules.
NITROUS OXIDE: A Serious Study Of
       A Laughing Matter
       HISTORY

       The English scientist and clergyman Joseph Priestly first

discovered Nitrous Oxide, an odorless and colorless gas, in 1793. Two

steps were taken by Priestly to create nitrous oxide. First, he had to

expose ammonium nitrate, and iron filings, to heat. Second the resulting gas, NO, was

passed through water to remove any toxic by-products. The reaction Priestly observed

looked like this:



                            2NO + H2 0 + Fe      N2 O + Fe(OH)2



After observing the gas, Priestly thought it could be used in preserving. This proved

unsuccessful. (Cameron and May, 1999)

       Picking up where Priestly left off, Humphrey Davy of the Pneumatic Institute in

Bristol England began to experiment with the compound. His main focus, however, was

the physiological properties of the gas, including the effects it has on respiration. Davy

began to test the gas on visitors to the institute. He found the effects to be quite funny and

thus named the chemical „laughing gas‟. “As nitrous oxide in its extensive operation

appears capable of destroying physical pain, it may probably be used with advantage

during surgical operations in which no great effusion of blood takes place”. (Cameron

and May, 1999)
        Even after Davy‟s research, nitrous oxide was only used for mere recreat ional

enjoyment and public shows. This continued for the next 40 years. In what were called

„Nitrous Oxide Capers‟, the public was allowed to inhale the gas for one minute and

enjoy its effects. Such events could be found in traveling medicine shows or carnivals.

Many famous and political figures, such as dignitaries from Clifton and Bristol, were

found taking advantage of Davy‟s purified nitrous oxide. (Cameron and May, 1999)

        STRUCTURE

        Nitrous Oxide is made up of two nitrogen atoms and an oxygen atom bonded in a linear

form. The two nitrogen atoms are connected by a double bond. The

double bond is the combination of a sigma bond of the S orbitals and a

pie bond of the P orbitals. An oxygen atom is bonded to the second

nitrogen atom also by a double bond. As individual atoms, the nitrogen atoms are identical.

However, when found in a nitrous oxide molecule, molecular orbitals begin to differ in energy as

well as which atomic orbitals contribute to this energy. This can be accounted for by their

proximity to the oxygen atom. For example, the second nitrogen atom, or N2 will be affected to a

greater degree by the oxygen atom because it is much closer. In order to see the effects of the

oxygen atom, you must observe the electron density model as well as the molecular orbitals.




        The coloring of this model represents the electron density at any given point. As you can

see, the oxygen at the end of the molecule has the most electro negativity and is, therefore,
attracting the electrons with the greatest pull. This model is a representation of how heavily the

oxygen will affect the electrons and atomic orbitals of the two nitrogen atoms. Regarding the

molecular orbitals, the HOMO, or highest occupied molecular orbital, is the orbital of the

molecule that has the highest, or least, negative energy. Negative energy is the energy that

attracts the electrons to the protons of the nucleus. Three interesting molecular orbitals of the

nitrous oxide molecule are the HOMO-7, the HOMO-4, and the HOMO-3. In the HOMO-7

orbital, all of the atoms in the molecule are contributing energy from the same atomic orbitals, the

S and the PZ orbitals. The HOMO-4 and HOMO-3 orbitals behave in a similar way. However,

they differ in that they consist of one positive ha lf and one negative half. The two halves are

symmetrical and split by the molecule along the longitudinal axis. (Left to Right: HOMO-3,

HOMO-4, HOMO-7)




            HOMO-3                           HOMO-4                              HOMO-7


        In comparing N2O and CO2, it is easy to see their likeness in their total molecular

energies.    N2O has a slightly less negative –182.606au energy while CO2 has –

186.561au. However, since the two molecules are isoelectronic, they both have the same

electron count, the electrons are just coming from different atoms. The different atoms

that make up the molecules can account for this slight change in energy. Aside from

atomic makeup, the physical structure of N2O and CO2 differ most in that, in the N2O
molecule the two nitrogen atoms are side by side, and in the CO2 molecule the carbon

atom separates the two oxygen atoms. The CO2 configuration, in which the one unique

atom separates the two common atoms, is more common than the N2O configuration.

This is one of the more peculiar properties of nitrous oxide.

        USE AS AN ANESTHETIC

        By the 1940s, nitrous oxide began to be used in clinical dentistry and in medicine as an

anesthetic. It was around then that Gardner Quincy Colton, a medical school dropout, began

putting on nitrous oxide exhibitions. At one of Colton‟s demonstrations in Hartford, Con necticut,

a certain volunteer inhaled the gas and proceeded to injure his leg when stumbling into a nearby

bench. The man was not aware of his injury until the effects of the gas wore off. A local dentist,

Dr. Horace Wells, was watching in the audience and became quite intrigued with this. He began

to consider nitrous oxide as a painkiller. After Colton‟s exhibition, he was invited to participate

in an experiment with Dr. Wells the following day. Colton administered the gas to Dr. Wells

while another dentist extracted one of Wells‟ molars. Dr. Wells felt no pain. This began the use

of nitrous oxide as a dental and medical painkiller. (Cameron and May, 1999)

                                           Dr. Wells attempted to demonstrate his discovery

                                   at the Harvard Medical School in Boston in January of

                                   1845.    A patient was anesthetized with nitrous oxide

                                   during a tooth extraction and still felt a mild amount of

                                   discomfort. Despite only feeling a small amount of pain,

Dr Wells‟ audience was not impressed and booed him from the stage. This incident

caused Dr. Wells to lose his reputation as a professional dentist and led to his suicide

three years later. Ironically, 150 years after the doctor‟s death, anesthesia in the form of
nitrous oxide became accepted by dental practices worldwide. Dr. Ho race Wells was

given the title of „Discoverer of Anesthesia‟. (Cameron and May, 1999)

          A SPEED BOOST FOR CARS

          Nitrous Oxide is un-reactive with alkali metals, halogens, ozone, and most other

substances when kept a room temperature. For this reason it is being used instead of CFCs as a

propellant in many aerosol cans. When exposed to large amounts of heat, however, nitrous oxide

decomposes exothermically into N 2 and O2 . The product of the reaction is lower in energy by

.052au.




                         -365.216au                     -365.268au




          This reaction can be made to occur in the combustion chamber of a car engine producing

3 moles of gas from 2. This in turn will provide the pistons with an extra

boost of power as well as liberate more heat from the engine. Many other

benefits can be observed by using nitrous oxide in automobiles. The

excess oxygen allows for more efficient fuel combustion, while the excess

nitrogen acts as a buffer to the increased cylinder pressure from the combustion. Also, the intake

temperature is reduced by the latent heat of vaporization of the nitrous oxide. These reasons

stated, it is quite common for nitrous oxide to be injected into the fuel lines of cars to provide an

exceptional boost of acceleration and speed. (Cameron and May, 1999)
        Dr. Horace Wells‟ research on the „laughing gas‟ discovered by Joseph Priestly has

impacted many people in more ways than one. Little did he know that his apparent failure in

using the gas as an anesthetic was actually a break through discovery. The use of nitrous oxide in

dentistry, as well as the practice of medicine, has made what would be unbearably painful

operations virtually painless to patients. Not to mention the rush it can give to your car, nitrous

oxide is a gas many have come to appreciate, even the recreational users. The effects of

„laughing gas‟ on the world are endless and as new studies are done who knows what the future

holds for this amusing gas.
REFERENCES



Cameron, Ewan and May, Paul. “A Boost For Fast Cars.”

  Internet. June 1999

  http://www.chm.bris.ac.uk/motm/n2o/n2oc.htm

Holley Inc. “Holley‟s Nitrous Oxide Systems (NOS) Brand”

  Internet. 1999

  http://www.holley.com/HiOctn/ProdLine/nos.html