High polarizability

In order for dipole—dipole and dipole-iaduced dipole iateractioas to be effective, the molecule must coataia polar groups and/or be highly polarizable. Ease of electronic distortion is favored by the presence of aromatic groups and double or triple bonds. These groups frequently are found ia the molecular stmcture of Hquid crystal compouads. The most common nematogenic and smectogenic molecules are of the type shown ia Table 2. 

The reactions of bis(trifluoromethyl)-subsatuted hetero 1,3 dienes are predomi nantly LLJMO controlled processes [238] With polar or highly polarizable dieno philes, the tendency to undergo stepwise cycloaddition reactions is considerable Notably these hetero-1,3-dienes react with a,(l unsaturated hetero multiple bond systems across the hetero multiple bond exclusively [243, 246 248] (equation 53)... 

Aprotic highly dipolar and highly polarizable (AHDP). 

Whereas this study focused on reaction protocol, the effect of the methylene source on selectivity was another important factor which demanded attention. Earlier studies have demonstrated that substitution of chloroiodomethane for diiodomethane leads to an increased reaction rate (Scheme 3.10) [22]. It is, thus, surprising that the use of chloroiodomethane in sub-protocol la leads a slower, less selective reaction. In contrast to the use of diiodomethane ( 100% conversion at 300 min), the reaction of chloroiodomethane only reaches 58% conversion after 300 min. Selectivity is severely reduced, dropping to 75 25 er. The failure of this reagent in the chiral process may be attributed to the obvious differences between the highly polarizable iodine and the more electronegative chlorine atom, although an exact analysis of the difference is not clear. 

Compounds composed of highly polarizing cations and highly polarizable... 

Soft Bases. The donor atoms are of low electronegativity and high polarizability and are easy to oxidize. They hold their valence electrons loosely. 

Soft Acids. The acceptor atoms are large, have low positive charge, and contain unshared pairs of electrons (p or d) in their valence shells. They have high polarizability and low electronegativity. 

ANSWER This compound has a sulfur atom with lone pairs. A lone pair on a sulfur atom will be strongly nucleophihc, even without a negative charge, because sulfur is large and highly polarizable. Strong nucleophiles favor Sn2 reactions. 

Molecular solids are aggregates of molecules bound together by intermolecular forces. Substances that are gases under normal conditions form molecular solids when they condense at low temperature. Many larger molecules have sufficient dispersion forces to exist as solids at room temperature. One example is naphthalene (Cio Hg), a white solid that melts at 80 °C. Naphthalene has a planar structure like that of benzene (see Section 10-), with a cloud of ten delocalized n electrons that lie above and below the molecular plane. Naphthalene molecules are held in the solid state by strong dispersion forces among these highly polarizable n electrons. The molecules in... 

A soft Lewis base has a large donor atom of high polarizability and low electronegativity. Iodide ion has its valence electrons in large a = 5 orbitals, making this anion highly polarizable and a very soft base. Other molecules and polyatomic anions with donor atoms from rows 3 to 6 are also soft bases. To summarize, the donor atom becomes softer from top to bottom of a column of the periodic table. 

A soft Lewis acid has a relatively high polarizability. Large atoms and low oxidation states often convey softness. Contrast with Hg , a typical soft acid. The ionic radius of Hg is 116 pm, almost twice the size of... 

In the general case, an incoming nucleophile would be expected to be favoured by (i) a high basicity consistent with ( ) a high polarizability, and the metal complex to favour its approach if (in) it contains electron-acceptive, or B class ligands. An interpretation of the available data may be essayed on these lines. The infrared data upon Ni(CO)4 are consistent with a weakening of the C-O bond , and it would be of interest to examine the solvent effect upon the Ni-C bond. 

The effect of highly polarizable cations on transport properties has scarcely been studied. Since the nitrate melts of Ag and TL are stable and have high polarizabilities, as shown in Table 5, their internal mobilities in binary mixtures containing one or both of these cations have been measured frequently. The isotherms are shown for and m,., in Figs. 10 and 11,... 

The Effeet of Highly Polarizable Cations on the Internal Mobility of the Seeond Cation in (Mi, M2)N03... 

Pearson (1966) defines a soft base as one in which the donor atom is of high polarizability and low electronegativity and is easily oxidized or associated with empty, low-lying orbitals . A hard base has opposite properties. The donor atom is of low polarizability and high electronegativity, is hard to reduce, and is associated with empty orbitals of high energy. ... 

Attractive forces arise from dipole interaction, a result of the fluctuations in the cloud of counterions. Although the mean distribution of counterions is uniform along the length of the polyion, there are fluctuations in the cloud of counterions which induce transient dipoles. When two polyions approach each other counterion fluctuations become coupled and enhance the attractive force. Since polyions have a high polarizability these attractive forces can be considerable. 

---