Acyclic structural properties

Compounds belonging to this series are of special interest because they exhibit the properties of both cyclic and acyclic structures as a result of ion complex tautomerism. They were obtained via borylation of hydroxy-alky lphosphines in the presence of tertiary amines [Eq. (64)], whereas primary and secondary amines give aminomethylphosphines under such conditions (84UK625 86JZV1641, 86MI1 90MI1). 

Physicochemical properties rather than reactivities were also explored. Molecular electrostatic potential (MEP) was calculated for the [l,2,4]triazolo[4,3- ]pyridine fragment 23, according to the CHELPG algorithm. This afforded a prediction of its H-bond acceptor ability in view of the synthesis of p38 MAP kinase inhibitors <2005JME5728>. Tautomerism was also examined for compound 24, also postulated as two possible acyclic structures. The ab initio self-consistent field (SCF)-calculated energies support 24a as the most stable tautomer <1999MRC493>. 

The polarity number p (or Wiener polarity number) was also defined by Wiener in 1947 [Wiener, 1947c] as the number of pairs of graph vertices which are separated by three edges. It is usually assumed that the polarity number accounts for the flexibility of acyclic structures, p being equal to the number of bonds around which free rotations can take place. Moreover, it relates to the steric properties of molecules. 

With its acyclic structure, large array of conjugated double bonds and important hydrophobicity, lycopene exhibits a range of unique and distinct biological properties. Of these properties, its antioxidant properties continue to arouse substantial interest. The system of conjugated double bonds allows lycopene molecules to... 

Ivanciuc, O., Ivanciuc, T. and Balaban, A.T. (2002c) Quantitative structure-property relationships for the normal boiling temperatures of acyclic carbonyl compounds. Internet Electron. J. Mol. Des., 1, 252-268. 

Because the podands were developed from the crown compounds and are seen as their open-chain analogues, properties similar to the crown compounds are to be expected for the podands. This is most evidently shown by the ability to form complexes.in case of the podands, they are called "podates or sometimes poda-plexes. ° This behavior of the podands to act as open-chained multidonor ligands was assessed with a variety of metallic and organic cations.However, due to the acyclic structure of the podands. as contrasted with the macrocyclic crown compounds, there are also differences in the behaviors of the two eompound types, including pros and cons. 

Next, we examine whether the match value Is able to rank structure candidates according to their relevance for the experimental spectrum. We generate all constitutional isomers of molecular formula C6H12O2,1313 candidates in total. If these are ordered by decreasing match values, the correct candidate methyl n-pentanoate Is at position 16. Figure 8.18 shows the 24 highest-ranked structure candidates and their match values. The top 13 positions are occupied by cyclic structures, although the ratio of cycUc and acyclic structures for 6 1202 is rather balanced (641 acyclic, 672 cycUc structures). If the acycUc nature could be determined somehow from the spectrum, then the correct candidate would be at position 2. In Section 8.5 we will try to find criteria for these structural properties empirically. 

The hyper-detour index can be obtained from the detour-path matrix. For acyclic graphs, the detour-path matrix is equal to the distance-path matrix, and consequently, the hyper-detour index for acyclic graphs is equal to the hyper-distance-path index obtained from the distance-path matrix. The hyper-detour index has been used in the structure property modeling of lower acyclic and cyclic saturated hydrocarbons with up to eight carbon atoms (Trinajstic et al., 2001). 

Dennis W. Smith Jr. joined The Dow Chemical Company Central Research Laboratory as Sr. Research Chemist in 1993, working primarily on the synthesis and characterization of high performance thermosets for thin film microelectronics applications. He then j oined Clemson in 1998 and was promoted to Professor of Chemistry in 2006, and in 2010, he joined the University of Texas at Dallas as Robert A. Welch Professor of Chemistry and was elected as Fellow of the American Chemical Society. His research interests include synthesis, mechanism, structure-property relationships, and applications of polymeric materials and composites. Smith received his BS from Missouri State University and his PhD from the University of Florida under the guidance of Prof. Ken Wagener on the scope and mechanism of acyclic diene metathesis (ADMET) polymerization. 

This chapter deals exclusively with the structural properties of ring compounds. Two kinds of destabilizing effects on rings are discussed. Torsional strain, the destabilizing effect of eclipsed carbon-hydrogen bonds, was mentioned in Chapter 2 when the acyclic hydrocarbons were discussed. The planar forms of ring... 

Oyumi, Y., Brill, T.B. and Rheingold, A.L. (198 ) Thermal Decomposition of Energetic Materials 20. A Comparison of The Structure Properties and Thermal Reactivity of an Acyclic and Cyclic Tetramethylenetetranitramine Pair Thermochiraica Acta 114, 209-225. 

Acyclic diene metathesis polymerization (ADMET) polymerization leads to polymers with precisely defined microstruetures and, hence, to excellent models to study the crystallization behavior of highly branehed ethylene copolymers. With ADMET, variation in the monomer structure gives access to a broad range of precisely defined polymers, allowing direet correlation of structure-property relationships. This clean polycondensation ehemistry is used here to produce a branched architecture characterized by the preeise branch placement every n fixed mefliylene units according to the following structural repeating unit ... 

Radical domino strategies have been scarcely described in the construction of polycyclic cyclopropanic structures. Indeed, radicals formed by 3-exo-trig cyclization are being rapidly reopened, and this property is notably used in radical clocks experiments. In order to suppress this unwanted event, Malacria and Fensterbank have devised a (dichloromethyl)dimethylsilyl ether able to play both roles of the initiation and termination sites of the radical process [108]. By designing an appropriate acyclic structure 98, the expected cyclopropanic compounds 99 have been obtained in good yields and diastereoselectivities after addition of MeLi to the silyloxycyclopentene intermediate (Scheme 5.35). 

Like propane, butanes are obtained from natural gas liquids and from refinery gas streams. The C4 acyclic paraffin consists of two isomers n-butane and isobutane (2-methylpropane). The physical as well as the chemical properties of the two isomers are quite different due to structural differences, for example, the vapor pressure (Reid method) for n-butane is 52 Ib/in., while it is 71 Ib/in. for isobutane. This makes the former a more favorable gasoline additive to adjust its vapor pressure. However, this use is declining in the United States due to new regulations that reduce the volatility of gasolines to 9 psi, primarily by removing butane. ... 

Comba and co-workers described a simple and efficient method for the determination of solution structures of weakly coupled binuclear copper(II) complexes.54 The technique involves the combination of molecular mechanics55,56 and EPR spectroscopy. From this standpoint they reported the structure of the complex (29). Using an acyclic tertiary tetraamine ligand, Bernhardt reported57 crystal structure of the complex (30), along with its redox properties. 

More than 600 different carotenoids from natural sources have been isolated and characterized. Physical properties and natural functions and actions of carotenoids are determined by their chemical properties, and these properties are defined by their molecular structures. Carotenoids consist of 40 carbon atoms (tetraterpenes) with conjugated double bonds. They consist of eight isoprenoid units j oined in such a manner that the arrangement of isoprenoid units is reversed at the center of the molecule so that the two central methyl groups are in a 1,6-position and the remaining nonterminal methyl groups are in a 1,5-position relationship. They can be acyclic or cyclic (mono- or bi-, alicyclic or aryl). Whereas green leaves contain unesterified hydroxy carotenoids, most carotenoids in ripe fruit are esterified with fatty acids. However, those of a few... 

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