What is the structure of nitrous oxide?
|Linear structure of N2O. Click on the picture for a 3D Chime model.|
Formal charge considerations suggest that the most important resonance structures are
A third structure involving a triple bond between the nitrogen and oxygen is unlikely because that would result in high formal charges. These resonance structures can be used to explain experimental bond lengths. The nitrogen-nitrogen bond is 1.126 Angstroms long which is slightly longer than the triple bond length in N2 (1.098 Angstroms). The nitrogen-oxygen bond is 1.186 Angstroms long. This is longer than the typical N=O bond (about 1.14 Angstroms), which agrees with the prediction of partial single-bond character for the NO bond in N2O.
The molecule is not strongly polar, despite the large electronegativity difference between nitrogen and oxygen. The resonance structures again can be used to explain why: the negative formal charge is concentrated on the terminal nitrogen in the structure at left,. The oxygen bears a negative formal charge in the other structure. Each structure is polar, but the dipole moments point in opposite directions. The dipole moment is expected to be small due to cancellation of the contributions from both structures.
The low polarity of the gas makes it both fat and water soluble. This allows it to travel through the bloodstream and into the fatty membranes of nerve cells where it produces its characteristic effects. Nitrous oxide's fat solubility and low toxicity make it an ideal propellant for whipped cream. It dissolves easily in cream under pressure and bubbles out of solution when the pressure is released, creating a fine creamy foam.
Over 20 years later, Humphry Davy wrote about the intoxicating effects of nitrous oxide, comparing them to the effects of alcohol. Breathing air after inhaling high concentrations of the gas sometimes lead to hysterical laughter. It also lead to a cessation of pain and "laughing gas" became the first artifical anaesthetic. It was in common use by surgeons in the late 19th century, and is still widely used in dentistry today.
N2O(g) N2(g) + O(g)The free oxygen atom quickly reacts with the fuel. A huge gain in horsepower results, since more fuel can be burned in less time.
If there is a large excess of nitrous oxide in the engine, the fuel will detonate. At the extremely high temperature produced by the explosion, oxygen atoms freed by decomposing N2O will attack the engine metal, severely damaging it.
Industrially the gas is prepared by gently heating ammonium nitrate [Archibald]:
NH4NO3(s) 2 H2O(g) + N2O(g)The preparation is dangerous because of N2O's tendency to explosively decompose into nitrogen and oxygen at high temperatures. (The World Trade Center and Oklahoma City bombings involved detonation of nitrous oxide produced by rapid high temperature decomposition.) N2O manufactured this way should NOT be inhaled, because it is contaminated with NO2 (a corrosive, irritating gas that can cause permanent lung and genetic damage!)
Another hazard of nitrous oxide stems from the fact that it is NOT an ideal gas. N2O molecules attract each other. The attractions require energy to break, so the expansion absorbs heat and the temperature of the gas plummets. A rapid expansion of nitrous oxide can cool it enough to cause frostbite. People doing whippets have actually frozen their lips, tongues, or vocal cords- and under the anaesthetic influence of nitrous oxide, the damage is done before any pain is felt.
Nitrous oxide has also been linked to birth defects, nerve damage, and permanent organ damage.
Author: Fred Senese firstname.lastname@example.org
Copyright © 1997-2010 by Fred Senese
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Last Revised 02/23/18.URL: http://antoine.frostburg.edu/chem/senese/101/inorganic/faq/print-laughing-gas.shtml