What is the formula for a primary amine?

A primary amine is characterized by the presence of one alkyl or aryl group attached to a nitrogen atom, which is further bonded to two hydrogen atoms. The chemical structure of a primary amine can be represented as R-NH2, where R denotes the organic group. This structure indicates that one side of the nitrogen is connected to a hydrocarbon chain (the R group) and the nitrogen atom itself is bonded to two hydrogen atoms.

It's important to differentiate this structure from other options. R-NH3 suggests a nitrogen atom bonded to three hydrogens, which is not consistent with the definition of a primary amine since it does not contain an organic substituent. R2-NH indicates a secondary amine with two organic groups bonded to the nitrogen and only one hydrogen. Lastly, R-NO2 represents a nitro group, not an amine, as it involves a nitrogen bonded to two oxygens and does not fit the description of an amine at all.

Thus, R-NH2 accurately represents the structure and classification of a primary amine.