Functional groups grouping organic compounds

Specific groups of atoms in an organic molecule can determine its physical and chemical properties. These groups are referred to as functional groups. Organic compounds which contain the functional group -OH, the hydroxyl group, are called alcohols. 

Functional Groups Organic compounds with similar fxmctional groups form a family of compounds and exhibit similar chemical and physical properties. For example, carboxylic acids behave as acids and therefore have low pH. Many esters, aldehydes, and ketones, especially those that contain an aromatic ring in their R group, tend to have pleasant smells. Amines, on the other hand, tend to have foul smells. 

For an organic compound with one functional group, a compound is water soluble only if it has five C atoms and contains an O or N atom. 

Table 24.4 summarizes the common functional groups, including the C=C and C C groups. Organic compounds commonly contain more than one functional group. Generally, the reactivity of a compound is determined by the number and types of functional groups in its makeup. 

Today, a number of different instrumental techniques are used to identify organic compounds. These techniques can be performed quickly on small amounts of a compound and can provide much more information about the compound s structure than simple chemical tests can provide. We have already discussed one such technique ultraviolet/visible (UVA/is) spectroscopy, which provides information about organic compounds with conjugated double bonds. In this chapter, we will look at two more instrumental techniques mass spectrometry and infrared (IR) spectroscopy. Mass spectrometry allows us to determine the molecular mass and the molecular formula of a compound, as well as certain structural features of the compound. Infrared spectroscopy allows us to determine the kinds of functional groups a compound has. In the next chapter, we will look at nuclear magnetic resonance (NMR) spectroscopy, which provides information about the carbon-hydrogen framework of a compound. Of these instrumental techniques, mass spectrometry is the only one that does not involve electromagnetic radiation. Thus, it is called spectrometry, whereas the others are called spectroscopy. 

Asher, W. E., Pankow, J. F., Erdakos, G. B., and Seinfeld, J. H. (2002) Estimating the vapor pressures of multi-functional oxygen-containing organic compounds using group contribution methods, Atmos. Environ. 36, 1483-1498. 

We can recognize many organic functional groups in compounds we use every day. Pesticides and Freons often contain chlorinated hydrocarbons. Many fruits get their aromas and flavors from aldehydes, ketones, and esters. The sour taste in foods is because of carboxylic acids, and the many rotting smells are due to amines (6.4-6.13). 

If a catalyst is to work well in solution, it (and tire reactants) must be sufficiently soluble and stable. Most polar catalysts (e.g., acids and bases) are used in water and most organometallic catalysts (compounds of metals witli organic ligands bonded to tliem) are used in organic solvents. Some enzymes function in aqueous biological solutions, witli tlieir solubilities detennined by the polar functional groups (R groups) on tlieir outer surfaces. 

---