section_path: Classification of organic compounds/Functional groups
section_name: Functional groups
paragraph_text: Functional groups
  
  The concept of functional groups is central in organic chemistry, both as a means to classify structures and for predicting properties. A functional group is a molecular module, and the reactivity of that functional group is assumed, within limits, to be the same in a variety of molecules. Functional groups can have a decisive influence on the chemical and physical properties of organic compounds. Molecules are classified based on their functional groups. Alcohols, for example, all have the subunit C-O-H. All alcohols tend to be somewhat hydrophilic, usually form esters, and usually can be converted to the corresponding halides. Most functional groups feature heteroatoms (atoms other than C and H). Organic compounds are classified according to functional groups, alcohols, carboxylic acids, amines, etc. Functional groups make the molecule more acidic or basic due to their electronic influence on surrounding parts of the molecule.
  
  As the p K (aka basicity) of the molecular addition/functional group increases, there is a corresponding dipole, when measured, increases in strength. A dipole directed towards the functional group (higher p K therefore basic nature of group) points towards it and decreases in strength with increasing distance. Dipole distance (measured in Angstroms) and steric hindrance towards the functional group have an intermolecular and intramolecular effect on the surrounding environment and pH level.
  
  Different functional groups have different p K values and bond strengths (single, double, triple) leading to increased electrophilicity with lower p K and increased nucleophile strength with higher p K. More basic/nucleophilic functional groups desire to attack an electrophilic functional group with a lower p K on another molecule (intermolecular) or within the same molecule (intramolecular). Any group with a net acidic p K that gets within range, such as an acyl or carbonyl group is fair game. Since the likelihood of being attacked decreases with an increase in p K, acyl chloride components with the lowest measured p K values are most likely to be attacked, followed by carboxylic acids (p K =4), thiols (13), malonates (13), alcohols (17), aldehydes (20), nitriles (25), esters (25), then amines (35). Amines are very basic, and are great nucleophiles/attackers.