Functional groups monofunctional

Linker molecules releasing one specific functional group ( monofunctional cleavage )... 

In order to produce a polymer by step addition and step condensation reactions it is necessary to start with precursors which each have at least two functional groups. Monofunctional reactants stop the formation of polymer chains and can be used to moderate polymer molecular weight. 

As noted in the text, chemists overwhelmingly use the nomenclature system devised and maintained by the International Union of Pure and Applied Chemistry, or IUPAC. Rules for naming monofunctional compounds were given throughout the text as each new functional group was introduced, and a list of where these rules can be found is given in Table A.l. 

The molecular weight can also be controlled by adding a monofunctional monomer. The monofunctional endgroup, B, has the same functionality as monomer BB. In this case, the moles of A functional groups in the difunctional... 

In order to obtain polymers tiiat are only end capped with the monofunctional end group, die moles of B functional groups must equal the moles of A functional groups. This is expressed in a second equation as... 

Relationship between Volume 9 and Previous Volumes. Compendium of Organic Synthetic Methods, Voiume 9 presents about 1200 examples of published reactions for the preparation of monofunctional compounds, updating the 10650 in Volumes 1-8. Volume 9 contains about 800 examples of reactions which prepare of difunctional compounds with various functional groups. Reviews have long been a feature of this series and Volume 9 adds almost 90 pertinent reviews in the various sections. Volume 9 contains approximately 1000 fewer entries than Volume 8 for an identical three-year period, primarily for difunctional compunds. Interestingly, there are about 500 fewer citations from the most cited journal (Tetrahedron Letters) than in the previous edition. Whether this represents a trend in the literature or an inadvertent selectivity on my part is unknown, but there has been a clear increase in biochemicai and total synthesis papers which may account for this. 

How to Use the Book to Locate Examples of the Preparation of Protection of Monofunctional Compounds. Examples of the preparation of one functional group from another are found in the monofunctional index on p. x, which lists the corresponding section and page. Sections that contain examples of the reactions of a functional group are found in the horizontal rows of this index. Section 1 gives examples of the reactions of alkynes that form new alkynes Section 16 gives reactions of alkynes that form carboxylic acids and Section 31 gives reactions of alkynes that form alcohols. 

Polar functional groups such as alcohols or phenols 11 or trimethylsilanol 4 are transformed by monofunctional silylating reagents Me3SiX 12 into their hpophilic and often volatile trimethylsilyl ethers 13 whereas water is converted into persilyl-ated water (=Me3SiOSiMe3, hexamethyldisiloxane, HMDSO, 7, b.p. 100 °C). The persilylation of phenols and, in particular, catechol (or hydroquinone) systems (Scheme 2.1) protects them efficiently against air oxidation even at temperatures of up to 180 °C. (cf, e.g., the silylation-amination of purine nucleosides with dopamine hydrochloride in Section 4.2.4)... 

X represents the combined number of both types of units in the polymer chain. Eq. (3) applies also to polymers stabilized (see Chap. Ill) with small amounts of monofunctional units, although here it becomes necessary to replace the extent of reaction p with another quantity, namely, the probability that a given functional group has reacted with a bifunctional monomer. Type ii polymers stabilized with an excess of one or the other ingredient will be discussed later. 

The procedure described here is not limited to the preparation of polymers such as 2. Starting from the difunctional silane 3 we have synthesized a copolymer, poly(dimethyl-co-isocyanopropylmethyl-siloxane) > as well as a linear homopolymer, poly(isocyanopropyl-methylsiloxane) 8 (Scheme 2). Indeed, preparation of a monofunctional analogue of 2. and h creates the potential for end-capping with an isocyanide function any polymer containing other functional groups, thereby in principle permitting mixed ligand complexes of polymers to be accessed. 

Monomers that participate in step growth polymerization may contain more or fewer than two functional groups. Difunctional monomers create linear polymers. Trifiinctional or polyfunctional monomers introduce branches which may lead to crosslinking when they are present in sufficiently high concentrations. Monofunctional monomers terminate polymerization by capping off the reactive end of the chain. Figure 2.12 illustrates the effect of functionality on molecular structure. 

The type of copolymer formed during step growth polymerization depends on the reactivity of the functional groups and the time of introduction of the comonomer. A random copolymer forms when equal concentrations of equally reactive monomers polymerize. The composition of the copolymer, then, will be the same as the composition of the reactants prior to polymerization. When the reactivities of the monomers-differ, the more highly reactive monomer reacts first, creating a block consisting predominandy of one monomer in the chain the lower reactivity monomer is added later. This assumes that there is no chain transfer and no monofunctional monomer present. If either of these conditions were to exist,... 

Telechelic polymers rank among the oldest designed precursors. The position of reactive groups at the ends of a sequence of repeating units makes it possible to incorporate various chemical structures into the network (polyether, polyester, polyamide, aliphatic, cycloaliphatic or aromatic hydrocarbon, etc.). The cross-linking density can be controlled by the length of precursor chain and functionality of the crosslinker, by molar ratio of functional groups, or by addition of a monofunctional component. Formation of elastically inactive loops is usually weak. Typical polyurethane systems composed of a macromolecular triol and a diisocyanate are statistically simple and when different theories listed above are... 

MONOFUNCTIONAL, which allow disconnections or FGI of "isolated" functional groups (that is to say, a functional group which does not belong to a bifunctional relationship, from 1,2-D up to 1,6-D). 

GROUP 2 MONOFUNCTIONAL (acts only on isolated functional groups)... 

The potentiometric titration curves of gels, which relate the pH of the exterior solution to the degree of ionization of the gel, resemble the titration curves of monofunctional acids or bases. However, the dissociation constants differ, often by two orders of magnitude, from the expected value for the functional group, and the slope of the curves is not the usual one. Addition of neutral salt changes the picture markedly and brings the curves closer to expectation. In the case of weak or medium... 

To date, only a few iridium catalysts have been applied to industrially relevant targets, especially on the larger scale. It is likely that several types of Ir catalyst are, in principle, feasible for technical applications in the pharmaceutical and agrochemical industries. At present, the most important problems are the relatively low catalytic activities of many highly selective systems and the fact, that relatively few catalysts have been applied to multifunctional substrates. For this reason, the scope and limitations of most catalysts known today have not yet been explored. For those in academic research, the lesson might be to employ new catalysts not only with monofunctional model compounds but also to test functional group tolerance and-as has already been done in some cases-to apply the catalysts to the total synthesis of relevant target molecules. 

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