nitrogen

Examples of nitrogen in the following topics:

• Properties of Nitrogen

  • Nitrogen in its elemental form is a non-metallic gas that makes up 78 percent of Earth's atmosphere.
  • Nitrogen compounds were well known during the Middle Ages.
  • Nitrogen is a chemical element with symbol N and atomic number 7.
  • Nitrogen is a nonmetal with an electronegativity of 3.04.
  • The triple bond in molecular nitrogen (N2) is one of the strongest known.

• Stereogenic Nitrogen

  • A close examination of the ephedrine and pseudoephedrine isomers suggests that another stereogenic center, the nitrogen, is present.
  • Since the nitrogen in these compounds is bonded to three different groups, its configuration is chiral.
  • However, pyramidal nitrogen is normally not configurationally stable.
  • If the nitrogen atom were the only chiral center in the molecule, a 50:50 (racemic) mixture of R and S configurations would exist at equilibrium.
  • In any event, nitrogen groups such as this, if present in a compound, do not contribute to isolable stereoisomers.

• Nitrogen Compounds

  • The nitrogen-nitrogen triple bond in N2 contains 226 kcal/mol of energy, making it one of the strongest bonds known.
  • When nitrogen gas is formed as a product from various reactions, the bond energy associated with the N-N triple bond is released, causing the explosive properties seen in many nitrogen compounds.
  • This is one of a variety of nitrogen oxides that form a family often abbreviated as NOx.
  • Nitrogen triiodide (NI3) is an extremely sensitive contact explosive.
  • In all cases, the explosive properties of nitrogen compounds are derived from the extreme stability of the product of these reactions: gaseous molecular nitrogen, N2.

• Nomenclature and Structure of Amines

  • Nitrogen atoms bonded to carbonyl groups, as in caffeine, also tend to be planar.
  • In contrast, atropine, coniine, morphine, nicotine and quinine have stereogenic pyramidal nitrogen atoms in their structural formulas (think of the non-bonding electron pair as a fourth substituent on a sp3 hybridized nitrogen).
  • In quinine this nitrogen is restricted to one configuration by the bridged ring system.
  • The two nitrogen atoms in Trögers base are the only stereogenic centers in the molecule.
  • With four different substituents, such a nitrogen would be a stable stereogenic center.

• Odd-Electron Molecules

  • Therefore, no matter how electrons are shared between the nitrogen and oxygen atoms, there is no way for nitrogen to have an octet.
  • Nitrogen dioxide is the chemical compound with the formula NO2.
  • Again, nitrogen dioxide does not follow the octet rule for one of its atoms, namely nitrogen.
  • Note the seven electrons around nitrogen.
  • It does not obey the octet rule on the nitrogen atom.

• Preparation of 1º-Amines

  • The general strategy is to first form a carbon-nitrogen bond by reacting a nitrogen nucleophile with a carbon electrophile.
  • In the second step, extraneous nitrogen substituents that may have facilitated this bonding are removed to give the amine product.
  • In the first two, an anionic nitrogen species undergoes an SN2 reaction with a modestly electrophilic alkyl halide reactant.
  • Since a carbocation is the electrophilic species, rather poorly nucleophilic nitrogen reactants can be used.
  • Here a strongly electrophilic nitrogen species (NO2(+)) bonds to a nucleophilic carbon compound.

• Dispersion Force

  • Van der Waals forces help explain how nitrogen can be liquefied.
  • Nitrogen gas (N2) is diatomic and non-polar because both nitrogen atoms have the same degree of electronegativity.
  • If there are no dipoles, what would make the nitrogen atoms stick together to form a liquid?

• Homonuclear Diatomic Molecules

  • Common diatomic molecules include hydrogen (H2), nitrogen (N2), oxygen (O2), and carbon monoxide (CO).
  • A space-filling model of the homonuclear diatomic molecule nitrogen.

• Other Reactions

  • Amides are very polar, thanks to the n-π conjugation of the nitrogen non-bonded electron pair with the carbonyl group.
  • When electrophiles bond to an amide, they do so at the oxygen atom in preference to the nitrogen.
  • As shown below, the oxygen-bonded conjugate acid is stabilized by resonance charge delocalization; whereas, the nitrogen-bonded analog is not.

• Amines

  • Amines are compounds characterized by the presence of a nitrogen atom, a lone pair of electrons, and three substituents.
  • The amine functional group contains a basic nitrogen atom with a lone pair of electrons.
  • Secondary amines are those that have two substituents and one hydrogen bonded to a nitrogen.
  • The general structure of an amine contains a nitrogen atom, a lone pair of electrons, and three substituents.
  • However, it is possible to have four organic substituents on the nitrogen, making it an ammonium cation with a charged nitrogen center.