Everything about Functional Group totally explained
In
organic chemistry,
functional groups are specific groups of
atoms within
molecules that are responsible for the characteristic
chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction(s) regardless of the size of the molecule it's a part of. However, its relative reactivity can be modified by nearby functional groups.
The word
moeity is often used synonymously to "functional group", but according to the IUPAC definition, a moiety is a half of a molecule including substructures of functional groups. For example, an
ester is divided into an alcohol and an acyl moiety, but has an ester functional group. The use of the word "moiety" to mean a functional group in the chemistry sense is actually fairly recent. While it has commonly been used in the archeology field to mean the half of a tribal family, it wasn't until a chance encounter between Elizabeth Bollwerk, an archeology graduate student, and a drug research scientist that the term made the cross-over.
Combining the names of functional groups with the names of the parent
alkanes generates a powerful
systematic nomenclature for naming
organic compounds.
The non-hydrogen atoms of functional groups are always associated with each other and with the rest of the molecule by
covalent bonds. When the group of atoms is associated with the rest of the molecule primarily by ionic forces, the group is referred to more properly as a
polyatomic ion or
complex ion. And all of these are called
radicals, by a meaning of the term
radical that predates the
free radical.
The first
carbon atom after the carbon that attaches to the functional group is called the
alpha carbon; the second, beta carbon, the third, gamma carbon, etc. If there's another functional group at a carbon, it may be named with the Greek letter, for example the gamma-amine in gamma-aminobutanoic acid is on the third carbon of the carbon chain attached to the carboxylic acid group.
Functional groups are attached to the carbon backbone of organic molecules. They determine the characteristics and chemical reactivity of molecules. Functional groups are far less stable than the carbon backbone and are likely to participate in chemical reactions.
Table of common functional groups
The following is a list of common functional groups. In the formulas, the symbols R and R' usually denote an attached hydrogen, or a
hydrocarbon side chain of any length, but may sometimes refer to any group of atoms.
Hydrocarbons
Functional groups that vary based upon the number and order of π bonds impart different chemistry. Each listing below contains C-H bonds, but each one differs in type (and scope) of reactivity.
Groups containing halogens
Haloalkanes are a class of molecule that's defined by a carbon-
halogen bond. This bond can be relatively weak (in the case of an iodoalkane) or quite stable (as in the case of a fluoroalkane). In general, with the exception of
fluorinated compounds, haloalkanes readily undergo
nucleophilic substitution reactions or
elimination reactions. The substitution on the carbon, the acidity of an adjacent proton, the solvent conditions, etc. all can influence the outcome of the reactivity.
Groups containing oxygen
Compounds that contain C-O bonds each possess differing reactivity based upon the location and
hybridization of the C-O bond, owing to the electron-withdrawing effect of sp² hybridized oxygen and the donating effects of sp³ hybridized oxygen.
Groups containing nitrogen
Compounds that contain Nitrogen in this category may contain C-O bonds, such as in the case of
amides.
Groups containing phosphorus and sulfur
Compounds that contain sulfur and phosphorus exhibit unique chemistry due to their ability to form more bonds than nitrogen and oxygen, their lighter analogues on the periodic table.
Other
- For a list of all functional groups:
Further Information
Get more info on 'Functional Group'.
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