Nomenclature and H-Bonding

ROH is an alcohol and ArOH is a phenol (Chapter 19). Some alcohols have common names, usually made up of the name of the alkyl group attached to the OH and the word alcohol e.g., ethyl ilcohol, C2H5OH. More generally the lUPAC method is used, in which the suffix -ol replaces the -e of the alkane to indicate the OH. The longest chain with the OH group is used as the parent, and the C bonded to the OH is called the carbinol carbon. 

Problem 13.1 Give a common name for each of the following alcohols and classify them as 1°. 2°, or 3°  

Problem 13.2 Name the following alcohols by the lUPAC method CHjCHjCH, 

Problem 13.4 Explain why (a) propanol boils at a higher temperature than the corresponding hydrocarbon b) propanol, unlike propane or butane, is soluble in H O (c) n-hexanol is not soluble in H O ( /) dimethyl ether (CH,OCH,) and ethyl alcohol (CH,CH,OH) have the same molecular weight, yet dimethyl ether has a lower boiling point (-24°C) than ethyl alcohol (78°C). M 

Propanol can H-bond intermolecularly. C,H,—O—H—O There is also a less important dipole-dipole 

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The fact that metal hydrides can be acidic may seem paradoxical in view of the nomenclature that insists that all complexes with a M-H bond be referred to as hydrides regardless of whether their reactivity is hydridic or not. Not only can some metal hydrides donate a proton, but some can be remarkably acidic. Some cationic dihydrogen complexes are sufficiently acidic to protonate Et20 [8], and some dicationic ruthenium complexes have an acidity comparable to or exceeding that of HOTf [9],... 

In the first approximation the changes of the water spectra by added ions is similar to a T-change of pure water. Once Bernal and Fowler67 have introduced quantitatively the nomenclature structure temperature 2"str of electrolyte solutions. rstr is the temperature of pure water with a similar H-bond content as the solution. The IR method gives a possibility to determine str quantitatively. 

Surfaces for X + M2 and M + X2.—The potential energy surfaces for the two exothermic reactions considered immediately above, F + H2 and H + F2, are repulsive in the nomenclature of Polanyi,14-15 i.e. a surface in which most of the exothermicity is released as the products separate. The other possible extreme of behaviour of a potential energy surface for an exothermic reaction is denoted by characterizing the surface as being of the early downhill or attractive type.14-15 In these systems, most of the exothermicity of reactions appears as vibrational excitation of the newly formed bond. The alkali metal (M), halogen (X) reactions of the type... 

The calculated results confirm that the 1-propanol molecule initially interacts with the Si(001)-(2 x 1) surface via the formation of a dative bond between the oxygen atom and the electrophilic down Si atom of the surface dimer. Specifically, the O-Si bond may be characterized as a covalent connection arising from the lone pair of the O atom. The 1-propanol molecule remains essentially intact (this motivates the nomenclature 1-1,1-2 and 1-3 for the physisorbed configurations) at the physisorbed sites, and the O-H bond assumes various orientations with respect to the Si surface. The obtained structures are shown in Figure 14-3 which illustrates that the direction of the O-H bond can be parallel (1-1), antiparallel (1-2) or perpendicular (1-3) to the Si dimer. However, the energies of the three configurations are very close to each other, i.e., the rotation of the 1-propanol molecule around the Si-O bond is quite facile. 

Intermolecular frequencies, calculated with various basis sets, are listed in Table 3.80. The authors point out that the normal modes are far from pure and that their nomenclature is very approximate. For example, the H-bond stretch contains a strong element of donor libration. Their designation of strain refers to simultaneous in-phase rotations of the two molecules, while they use the term bend to indicate out-of-phase rotations. The imaginary frequencies of the torsional modes are evidence that the true equilibrium geometry of the formamide dimer is nonplanar. The mode appears at about 120 cm , a little smaller than that for H2CO---HOH where a water molecule donates a proton to the carbonyl oxy-... 

A later calculation disputed these results in that anti-anti was computed to be the most stable conformer . This work, however, was limited to the SCF level, using a 6-31 -I- -l-G basis set. (If consulting the original paper, it is important to note that this set of workers reversed the standard nomenclature for syn and anti.) Anti-syn was computed to be somewhat less stable, followed by syn-anti and syn-syn. These results were compared to a statistical survey of such interactions in proteins where a marked propensity was observed for the syn-syn structure, the least stable in the gas phase. In contrast, the anti-anti configuration, most stable in the gas phase, is observed rarely in proteins. The authors attributed these discrepancies to crystal packing forces. There also seems to be a preference in the crystals for centrosymmetric (or nearly so) Fl-bonds between carboxyl and carboxy-late, although noncentrosymmetric H-bonds are also present in large numbers. Centrosym-... 

Chart 11.4 Nomenclature of C—H activation via metal insertion into C—H bond and the microscopic reverse reaction. (Note The term oxidative addition is used for the single step of metal insertion into a coordinated C—H bond as well as the overall two-step process of C—H coordination followed by metal insertion into the C—H bond.)... 

Indeed, using the proposed nomenclature affords an illustrative and realistic picture of the geometry and interaction within the host-guest unit. But keep in mind, it requires knowledge of structural details, at best of the crystal structure. If so, a very precise characterization via name is possible, e.g. going into detailed H-bonding networks of crystal inclusions (Fig. 15) which are ... 

In principle, a core is always totally encapsulated by at least one valence basin and therefore propositions i) and ii) are redundant when / tends to zero unless the valence localization domains and a core domain have already merged into a single domian. In our description of the chemical bond a basin which contains a proton is considered as a valence basin except for the peculiar case of the very strong hydrogen bond for which a pseudo core shell is found around the bridging proton. The valence basins are therefore divided into mono-, di- and polysynaptic ones. As an example, a C-H bond is characterized by a disynaptic basin which encompasses the proton and shares a common separatrix with the carbon core basin. The nomenclature adopted to label core and valence attractors and basins is given in table 1. The attractors and basins are labeled as T[,](atom labels). T denotes... 

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