Positive charge of NAD+ molecule

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SUMMARY

The positive charge of the NAD+ molecule is located on the nitrogen atom in the nicotinamide group due to its bonding configuration. Despite having four bonds, the nitrogen atom possesses a lone pair of electrons, which contributes to its positive charge upon protonation by H+. The formal charge calculation reveals that nitrogen, with 4 bonding electrons and 2 inner shell electrons, results in a net positive charge when compared to its 7 protons. This understanding is crucial for comprehending the molecular behavior of NAD+ in biochemical reactions.

PREREQUISITES
  • Understanding of Lewis dot structures
  • Knowledge of protonation and its effects on molecular charge
  • Familiarity with formal charge calculations
  • Basic concepts of molecular bonding and electron configuration
NEXT STEPS
  • Study Lewis structures for various organic molecules
  • Learn about protonation effects in biochemical pathways
  • Explore formal charge calculations in complex molecules
  • Investigate the role of NAD+ in cellular metabolism
USEFUL FOR

Chemistry students, biochemists, and molecular biologists interested in the structural and functional properties of NAD+ and its role in metabolic processes.

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Why is the positive charge of the NAD+ molecule located on the nitrogen in the nicotinamide group? This nitrogen has 4 bonds attached to it, but nitrogen only has 3 holes in its valence shell, so wouldn't this make a negative charge on this nitrogen?
 
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tickle_monste said:
Why is the positive charge of the NAD+ molecule located on the nitrogen in the nicotinamide group? This nitrogen has 4 bonds attached to it, but nitrogen only has 3 holes in its valence shell, so wouldn't this make a negative charge on this nitrogen?

Draw the lewis dot structure for the nitrogen in this system and you will see a free lone pair of electrons before protonation by H+. Is it true that when you protonate a neutral molecule with H+ you are left with an anion?
 
In general, for determining the formal charge on an atom, we consider all of the electrons in lone pairs and inner shells as belonging to that atom as well ashalf of the electrons in chemical bonds as belonging to that atom. Therefore, the nitrogen has 4 bonds attached to it (giving 4 electrons) plus two inner shell electrons, giving a total of 6 electrons to nitrogen's 7 protons.
 

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