tailieunhanh - Functional Groups and Chemical Families

Prepare calibration standards at a minimum of three concentration levels for each parameter of interest by adding volumes of one or more stock standards to a volumetric flask. To each calibration standard, add a known constant amount of one or more internal standards, and dilute to volume with mobile phase. One of the standards should be at a concentration near, but above, the MDL and the other concentrations should correspond to the expected range of concentrations found in real samples or should define the working range of the detector | Functional Groups and Chemical Families Although there are a wide variety of organic compounds most of them are composed of the elements from the upper right hand portion of the periodic chart C H N O S Halogen. These compounds can be categorized by certain structural and reactive features dictated by the way carbon bonds to itself or another element . carbon double bonded to oxygen. Such a grouping of compounds provides us with the concept of chemical families. These special bonding arrangements have different reactivities or functions and associated with each family is particular functional group. Rigorously speaking the functional group is not the whole molecule but only that collection of atoms that provides a specific chemical function. For example the chemical family of alcohols is characterized by the function of the hydroxyl OH group and aldehydes ketones are characterized by carbonyl groups C O . There are various combinations of hydroxyl groups in molecules along with carbonyl groups and these combinations can lead to hydroxyketones and aldehydes the basis for sugars as well as to carboxylic acids. Indeed esters and amides also have carbonyl groups C O but differ in their combination with an additional structural feature. To understand the reactivity of chemical families one must consider the interplay between the various structural features in that molecule and identifying the fundamental functional groups is a good place to start. Within a given family family members are arranged by the length of the longest carbon chain. Typically an organic compound will have a base name composed of a suffix to identify the family and a prefix to identify the length of the longest carbon chain. The first 10 prefixes are meth- 1 hex- 6 eth- 2 hept- 7 prop- 3 oct- 8 but- 4 non- 9 pent- 5 dec- 10 The following provides a list of the more common chemical families exemplified as their pentmember. Hydrocarbons all C H Alkanes 1 Molecular formula CnH2n 2 C5H12 pentane .