Reactivity, functional groups and

Much of Chapter 3 has been devoted to how a functional group determines the strength of inter-molecular forces and, consequently, the physical properties of molecules. A functional group also determines reactivity. What type of reaction does a particular kind of organic compound undergo Begin by recalling two fundamental concepts. 

All functional groups contain a heteroatom, a n bond, or both, and these features make electron-deficient (or electrophilic) sites and electron-rich (or nucleophilic) sites in a molecule. Molecules react at these sites. To predict reactivity, first locate the functional group and then determine the resulting electron-rich or electron-deficient sites it creates. Keep three guidelines in mind. 

A lone pair on a heteroatom makes it basic and nucleophilic. 

All functional groups contain a heteroatom, a 7C bond, or both, and these features make electron-deficient (or electrophilic) sites and electron-rich (or nucleophilic) sites in a mol- 

Problem 3.17 Label the electrophilic and nucleophilic sites in each molecule. 

By identifying the nucleophilic and electrophilic sites in a compound you can begin to understand how it will react. In general, electron-rich sites react with electron-deficient sites  

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Even so, a number of chemical agents, including liquids, chemically attack polymers. Reactions that would ordinarily occur with small molecules also occur in polymers, given the same functional groups and reactive sites. Thus benzene, toluene, etc., are readily sulfonated when exposed to sulfuric acid. Likewise polystyrene (PS) is sulfonated when exposed to liquids and gases containing sulfuric acid ... 

Five specific mechanisms have been identified as those that disturb proper development. These include interaction with hormone receptors, covalent bonding to DNA, degradation of cell membranes or proteins, enzyme inhibition, and protein modification by interference with sulfhy-dryl groups. E It is important to note that teratogens with widely differing functional groups and reactivities can produce identical developmental effects. It is also noteworthy that mixtures of teratogens can simultaneously disturb more than one developmental mechanism and induce effects not expected from the actions of the mixture components. 

Starting with the concept molecule we can define a relationship to structure with the relational term consists of. Following the route we can relate structure to substructure, and to functional group. Here we introduce the new relation term defines to describe the relationship between functional group and reactivity. As we follow through all cross-references, we build up a complex picture of the concept of molecule and its relations to other concepts, like biological activity. 

Polyurethane [6], polyurea, and epoxy resin [7] are obtained by polyaddition polymerization. Formation of crosslinks depends on reaction conditions. It is complex because, in many cases, both the combination of various addition reactions and condensation contribute, and the number of functional groups and reactivities change. 

Introduction of Non-functional Alkyl and Reactive Allyl Groups... 

Our first three chapters established some fundamental principles concerning the structure of organic molecules and introduced the connection between structure and reactivity with a review of acid-base reactions In this chapter we explore structure and reactivity m more detail by developing two concepts functional groups and reaction mechanisms A functional group is the atom or group m a molecule most respon sible for the reaction the compound undergoes under a prescribed set of conditions How the structure of the reactant is transformed to that of the product is what we mean by the reaction mechanism... 

One mode of chemical reactivity involves the ring itself as a functional group and includes... 

Antioxidants markedly retard the rate of autoxidation throughout the useful life of the polymer. Chain-terminating antioxidants have a reactive —NH or —OH functional group and include compounds such as secondary aryl amines or hindered phenols. They function by transfer of hydrogen to free radicals, principally to peroxy radicals. Butylated hydroxytoluene is a widely used example. 

Monomers containing reactive functional groups ia the ester moiety exhibit the toxicological profile of the functional group and should be considered on an iadividual basis. Consideration of methods of monomer manufacture may be appropriate, as by-products, even at trace levels, may affect the observed biological response. 

Acrylamide has two functional groups, a reactive double bond and an amide group. It undergoes many reactions typical of the two functionalities [1,2]. The... 

The number-average molecular weight of a polymer may be controlled by offsetting the stoichiometry of two dissimilar mutually reactive difunctional monomers. The polymer will have the same endgroup functionality as that of the monomer used in excess. For a generic polymer made from a difunctional monomer AA with A functional groups and an excess of difunctional monomer BB widt B functional groups, r is defined as... 

Step-growth polymerization processes must be carefully designed in order to avoid reaction conditions that promote deleterious side reactions that may result in the loss of monomer functionality or the volatilization of monomers. For example, initial transesterification between DMT and EG is conducted in the presence of Lewis acid catalysts at temperatures (200°C) that do not result in the premature volatilization of EG (neat EG boiling point 197°C). In addition, polyurethane formation requires the absence of protic impurities such as water to avoid the premature formation of carbamic acids followed by decarboxylation and formation of the reactive amine.50 Thus, reaction conditions must be carefully chosen to avoid undesirable consumption of the functional groups, and 1 1 stoichiometry must be maintained throughout the polymerization process. 

This section deals with reactions which involve only the organo-ligand, whether unmodified or modified by the loss or gain of a proton, and the cobalt. After considering established and possible mechanisms (Section B,l) we list examples to show how reactivity is influenced by different functional groups and substituents (Section B,2), and by changes in the axial and equatorial ligands (Section B,3). 

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