Chemical groups functionalities

Chemical bonds are formed by electrons, and formation or breakage of bonds requires the migration of electrons. In broad terms, reactive chemical groups function either as electrophiles or as nucleophiles. Electrophiles are electron-deficient substances that react with electron-rich substances nucleophiles are electron-rich substances that react with electron-deficient substances. The task of a catalyst often is to make a potentially reactive group more reactive by increasing its electrophilic or nucleophilic character. In many cases the simplest way to do this is to add or remove a proton. 

Chemical group Functional group Region (cm ) Strength... 

Acrolein, acrylamide, hydroxyalkyl acrylates, and other functional derivatives can be more hazardous from a health standpoint than acryhc acid and its simple alkyl esters. Furthermore, some derivatives, such as the alkyl 2-chloroacrylates, are powerful vesicants and can cause serious eye injuries. Thus, although the hazards of acryhc acid and the normal alkyl acrylates are moderate and they can be handled safely with ordinary care to industrial hygiene, this should not be assumed to be the case for compounds with chemically different functional groups (see Industrial hygiene Plant safety Toxicology). 

In contrast, aromatic ketones are high boiling, colorless Hquids that generally have a fragrant odor and are almost insoluble in water. They are useful as intermediates in chemical manufacture. Functionalized and cycHc ketones are also good solvents. Ring size and the type and location of functional groups affect odor, color, and reactivity of these ketones. 

There are no simple rules for chemically defining a good odorant. Table 2 and Figure 1 present a number of widely used aroma chemicals by chemical type. Table 2. Typical Aroma Chemicals by Functional Group... 

In addition to data obtained using the spectral mode of analysis, it is often important to know the location of a particular chemical group or compound on the sample surface. Such information is achieved by static SIMS chemical mapping—a procedure in which a specific chemical functionality on the material is imaged, providing information as to its lateral distribution on the surface. 

Organofunctional silane Chemical structure of organofunctional group Functional groups used... 

Because of the unambiguous reactive sites of monomers and the high chemo-and stereoselectivity of transition-metal-catalyzed coupling reactions, polymers prepared by transition metal coupling have predictable chemical structures. Functional groups can be easily and selectively introduced at the desired position within die polymer chains. Therefore, polymers widi specific properties can be rationally designed and synthesized. 

Proteins may be classified on the basis of the solubility, shape, or function or of the presence of a prosthetic group such as heme. Proteins perform complex physical and catalytic functions by positioning specific chemical groups in a precise three-dimensional arrangement that is both functionally efficient and physically strong. 

It is usually desirable to define molecular weights by analyzing underivatized samples, because chemically labile functional groups will then be observed. Unfortunately, underivatized oligosaccharides often give ambiguous sequence-data. The reasons for this may be deduced from a... 

When making theoretical considerations of polycondensation processes it is necessary to distinguish chemically identical functional groups if they differ in reactivity. Examples are primary and secondary hydroxyls in a molecule of glycerine, SA2j A2, which belong to kinetically distinct types Ax and A2. 

Ionization. Many organic chemicals contain functional groups that dissociate to yield charged species. The toxicity and chemical reactivity of the uncharged (neutral) molecule and its charged ions can be very different. Differences in reactivity of ionic species can be accommodated in fate models when rate constants are expressed in terms of the individual species. 

---