Secondary is a term used in

organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic matter, organic materials, i.e., matter in its various forms that contain ...

to classify various types of compounds (e. g. alcohols, alkyl halides, amines) or reactive intermediates (e. g. alkyl radicals, carbocations). An atom is considered secondary if it has two 'R' Groups attached to it. An 'R' group is a carbon containing group such as a

methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula (whereas normal methane has the formula ). In formulas, the group is often abbreviated as ...

(CH₃). A secondary compound is most often classified on an alpha carbon (middle carbon) or a nitrogen. The word secondary comes from the root word 'second' which means two. This

nomenclature Nomenclature (, ) is a system of names or terms, or the rules for forming these terms in a particular field of arts or sciences. (The theoretical field studying nomenclature is sometimes referred to as ''onymology'' or ''taxonymy'' ). The principl ...

can be used in many cases and further used to explain relative reactivity. The reactivity of molecules varies with respect to the attached atoms. Thus, a primary, secondary, tertiary and quaternary molecule of the same function group will have different reactivities.

Secondary alcohols

Secondary alcohols have the formula RCH(OH)R' where R and R' are organyl.

Secondary amines

A secondary amine has the formula RR'NH where R and R' are organyl.

Secondary amides

Secondary amides have the formula RC(O)NHR' where R can be H or organyl and R' is organyl. which is the loss of the single proton bonded to the middle nitrogen.

Secondary phosphines

Secondary phosphines have two 'R' groups attached to a phosphorus atom and again, a P-H bond.

Further uses

"Secondary" is a general term used in chemistry that can be applied to many molecules, even more than the ones listed here; the principles seen in these examples can be further applied to other functional group containing molecules. The ones shown above are common molecules seen in many organic reactions. By classifying a molecule as secondary it then be compared with a molecule of primary or tertiary nature to determine the relative reactivity.

References