group

Examples of group in the following topics:

• Functional Groups

  • Functional groups are atoms or small groups of atoms (two to four) that exhibit a characteristic reactivity when treated with certain reagents.
  • A particular functional group will almost always display its characteristic chemical behavior when it is present in a compound.
  • Because of their importance in understanding organic chemistry, functional groups have characteristic names that often carry over in the naming of individual compounds incorporating specific groups.
  • In the following table the atoms of each functional group are colored red and the characteristic IUPAC nomenclature suffix that denotes some (but not all) functional groups is also colored.

• Functional Groups

  • In organic chemistry, a functional group is a specific group of atoms or bonds within a compound that is responsible for the characteristic chemical reactions of that compound.
  • Functional groups also play an important part in organic compound nomenclature; combining the names of the functional groups with the names of the parent alkanes provides a way to distinguish compounds.
  • Functional groups play a significant role in directing and controlling organic reactions.
  • Alcohols are a common functional group (-OH).
  • Define the term "functional group" as it applies to organic molecules

• By Functional Group

  • Functional groups are atoms or small groups of atoms (usually two to four) that exhibit a characteristic reactivity when treated with certain reagents.
  • A particular functional group will almost always display its characteristic chemical behavior when it is present in a compound.
  • Because of this, the discussion of organic reactions is often organized according to functional groups.
  • The following table summarizes the general chemical behavior of the common functional groups.
  • For reference, the alkanes provide a background of behavior in the absence of more localized functional groups.

• Group Frequencies

  • Detailed information about the infrared absorptions observed for various bonded atoms and groups is usually presented in tabular form.
  • The following table provides a collection of such data for the most common functional groups.
  • Infrared absorption data for some functional groups not listed in the preceding table are given below.

• Related Carbonyl Derivatives

  • Other functional group combinations with the carbonyl group can be prepared from carboxylic acids, and are usually treated as related derivatives.
  • As in the case of amines, amides are classified as 1º, 2º or 3º, depending on the number of alkyl groups bonded to the nitrogen.
  • Functional groups of this kind are found in many kinds of natural products.
  • Some examples are shown below with the functional group colored red.
  • The Greek letter locates the nitrogen relative to the carbonyl group of the amide.

• Nomenclature of Carboxylic Acids

  • The carboxyl functional group that characterizes the carboxylic acids is unusual in that it is composed of two functional groups described earlier in this text.
  • As may be seen in the formula below, the carboxyl group is made up of a hydroxyl group bonded to a carbonyl group.
  • Other combinations of functional groups were described previously, and significant changes in chemical behavior as a result of group interactions were described (e.g. phenol & aniline).
  • As with aldehydes, the carboxyl group must be located at the end of a carbon chain.
  • For this group of compounds one such phrase is: "Oh My Such Good Apple Pie".

• Alcohol Reactions

  • The functional group of the alcohols is the hydroxyl group, –OH.
  • Unlike the alkyl halides, this group has two reactive covalent bonds, the C–O bond and the O–H bond.
  • Consequently, the covalent bonds of this functional group are polarized so that oxygen is electron rich and both carbon and hydrogen are electrophilic, as shown in the drawing below.
  • Indeed, the dipolar nature of the O–H bond is such that alcohols are much stronger acids than alkanes (by roughly 1030 times), and nearly that much stronger than ethers (oxygen substituted alkanes that do not have an O–H group).
  • The most reactive site in an alcohol molecule is the hydroxyl group, despite the fact that the O–H bond strength is significantly greater than that of the C–C, C–H and C–O bonds, demonstrating again the difference between thermodynamic and chemical stability.

• Alcohols

  • Alcohols are functional groups characterized by the presence of an -OH group.
  • Alcohols are organic compounds in which the hydroxyl functional group (-OH) is bound to a carbon atom.
  • The presence of the -OH groups allows for hydrogen bonding with other -OH groups, hydrogen atoms, and other molecules.
  • Hydroxyl groups alone are not considered good leaving groups.
  • Alcohols are characterized by the presence of an -OH group, which is generally in a bent shape, like that of water.

• Alkanes

  • Examples of some common alkyl groups are given in the following table.
  • Note that the "ane" suffix is replaced by "yl" in naming groups.
  • The symbol R is used to designate a generic (unspecified) alkyl group.
  • Number the chain consecutively, starting at the end nearest a substituent group.
  • Designate the location of each substituent group by an appropriate number and name.

• Variation of Physical Properties Within a Group

  • In chemistry, a group is a vertical column in the periodic table of the chemical elements.
  • Different groups exhibit different trends in boiling and melting points.
  • For Groups 1 and 2, the boiling and melting points decrease as you move down the group.
  • In the main group elements, the boron and carbon families (Groups 13 and 14) decrease in their boiling and melting points as you move down the group, whereas the nitrogen, oxygen, and fluorine families (Groups 15, 16, and 17) tend to increase in both.
  • The noble gases (Group 18) decrease in their boiling and melting points down the group.