Cyclic functional groups

Acyclic Core Group Equivalents of Cyclic Functional Groups.67... 

Formation of polymer chains or networks from these compounds can be conceived either as a ring-opening polymerization process or a polyreaction involving exo-cyclic functional groups. 

Block copolymers of vinyl acetate with methyl methacrylate, acrylic acid, acrylonitrile, and vinyl pyrrolidinone have been prepared by copolymerization in viscous conditions, with solvents that are poor solvents for the vinyl acetate macroradical (123). Similady, the copolymerization of vinyl acetate with methyl methacrylate is enhanced by the solvents acetonitrile and acetone and is decreased by propanol (124). Copolymers of vinyl acetate containing cyclic functional groups in the polymer chain have been prepared by copolymerization of vinyl acetate with IV,IV- diallylcyan amide and N,N-diallylamine (125,126). 

Of the general formula, R - S — H, where R represents an aliphatic or cyclic radical, the thiols —also known as mercaptans— are acidic in behavior owing to their S—H functional group they are corrosive and malodorous. Their concentration in crude oils is very low if not zero, but they are created from other sulfur compounds during refining operations and show up in the light cuts, as illustrated in Table 8.6. 

Regioselectivity of C—C double bond formation can also be achieved in the reductiv or oxidative elimination of two functional groups from adjacent carbon atoms. Well estab llshed methods in synthesis include the reductive cleavage of cyclic thionocarbonates derivec from glycols (E.J. Corey, 1968 C W. Hartmann, 1972), the reduction of epoxides with Zn/Nal or of dihalides with metals, organometallic compounds, or Nal/acetone (seep.lS6f), and the oxidative decarboxylation of 1,2-dicarboxylic acids (C.A. Grob, 1958 S. Masamune, 1966 R.A. Sheldon, 1972) or their r-butyl peresters (E.N. Cain, 1969). 

Hydrocarbons that contain a carbon-carbon triple bond are called alkynes Non cyclic alkynes have the molecular formula C H2 -2 Acetylene (HC=CH) is the simplest alkyne We call compounds that have their triple bond at the end of a carbon chain (RC=CH) monosubstituted or terminal alkynes Disubstituted alkynes (RC=CR ) have internal triple bonds You will see m this chapter that a carbon-carbon triple bond is a functional group reacting with many of the same reagents that react with the double bonds of alkenes... 

Compounds that contain both carbonyl and alcohol functional groups are often more stable as cyclic hemiacetals or cyclic acetals than as open chain compounds Examples of several of these are shown Deduce the structure of the open chain form of each... 

Aldoses incorporate two functional groups C=0 and OH which are capable of react mg with each other We saw m Section 17 8 that nucleophilic addition of an alcohol function to a carbonyl group gives a hemiacetal When the hydroxyl and carbonyl groups are part of the same molecule a cyclic hemiacetal results as illustrated m Figure 25 3 Cyclic hemiacetal formation is most common when the ring that results is five or SIX membered Five membered cyclic hemiacetals of carbohydrates are called furanose forms SIX membered ones are called pyranose forms The nng carbon that is derived... 

Although carbohydrates exist almost entirely as cyclic hemiacetals m aqueous solution they are m rapid equilibrium with their open chain forms and most of the reagents that react with simple aldehydes and ketones react m an analogous way with the carbonyl functional groups of carbohydrates... 

Carbohydrates are marvelous molecules In most of them every carbon bears a functional group and the nature of the functional groups changes as the molecule mterconverts between open chain and cyclic hemiacetal forms Any approach to understanding carbohydrates must begin with structure... 

Frosts circle (Section 11 19) A mnemonic that gives the Huckel TT MOs for cyclic conjugated molecules and 10ns Functional class nomenclature (Section 4 2) Type of lUPAC nomenclature in which compounds are named according to functional group families The last word in the name... 

Cycloaliphatic amines are comprised of a cyclic hydrocarbon stmctural component and an amine functional group external to that ring. Included in an extended cycloaUphatic amine definition ate aminomethyl cycloaUphatics. Although some cycloaUphatic amine and diamine products have direct end use apphcations, their major function is as low cost organic intermediates sold as moderate volume specification products. 

Some heterocyclic compounds are at the same time cyclic examples of common functional groups. In such cases, they may be so named, and radicals derived from them may be derived accordingly, as in (164). 

However, certain additives can decrease the rate of thermal decomposition [28]. These additives include cyclic sulfates, sulfones, sultones, aliphatic and aromatic anhydrides, and polymers with pendant carboxylic acid functional groups. Most of these materials are latent acids, which decompose on heating in the presence of moisture to form a strong acid, as shown for cyclic sulfate, 9, in Eq. 5. 

During electrochemical fluorination retention of important functional groups or atoms in molecules is essential. Acyl fluorides and chlorides, but not carboxylic acids and anhydrides (which decarboxylate), survive perfluorination to the perfluorinated acid fluorides, albeit with some cyclization in longer chain (>C4) species [73]. Electrochemical fluorination of acetyl fluoride produces perfluoro-acetyl fluoride in 36-45% yields [85]. Electrochemical fluorination of octanoyl chloride results in perfluorinated cyclic ethers as well as perfluorinated octanoyl fluonde. Cyclization decreases as initial substrate concentration increases and has been linked to hydrogen-bonded onium polycations [73]. Cyclization is a common phenomenon involving longer (>C4) and branched chains. a-Alkyl-substituted carboxylic acid chlorides, fluorides, and methyl esters produce both the perfluorinated cyclic five- and six-membered ring ethers as well as the perfluorinated acid... 

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