Substituent groups bonds

The triaLkoxy(aryloxy)boranes are typically monomeric, soluble in most organic solvents, and dissolve in water with hydrolysis to form boric acid and the corresponding alcohol and phenol. Although the rate of hydrolysis is usually very fast, it is dependent on the bulk of the alkyl or aryl substituent groups bonded to the boron atom. Secondary and tertiary alkyl esters are generally more stable than the primary alkyl esters. The boron atom in these compounds is in a trigonal coplanar state with bond hybridization. A vacantp orbital exists along the threefold axis perpendicular to the BO plane. 

Anisotropy is observed when a substituent group bonds a carbonyl group directly to the benzene ring (Fig. 7.61). Once again, the ring protons fall into two groups, with the ortho protons downfield from the metalpara protons. Benzaldehyde (Fig. 7.62) and acetophenone both show this effect in their NMR spectra. A similar effect is sometimes observed when a carbon-carbon double bond is attached to the ring. The 300-MHz spectrum of benzaldehyde (Fig. 7.62b) is a nearly first-order spectrum (probably a deceptively simple AA BB C spectrum) and shows a doublet (He, 2 H), a triplet (Hb, 1 H), and a triplet (Ha, 2 H). 

The E, Z system is a system of nomenclature used to describe the arrangement of substituent groups bond to the C atoms of a carbon-carbon double bond. 

Lines 4—18 form the connection table (Ctah), containing the description of the collection of atoms constituting the given compound, which can be wholly or partially connected by bonds. Such a collection can represent molecules, molecular fragments, substructures, substituent groups, and so on. In case of a Molfile, the Ctah block describes a single molecule. 

The substituent groups on the double bonds of most alkenes are of course more com plicated than m this example The rules for ranking substituents especially alkyl groups are described m Table 5 1... 

Positive Z values indicate a downfield shift, and an arrow indicates the point of attachment of the substituent group to the double bond. 

Substituents on both sides of the double bond are considered separately. Additional vinyl carbons are treated as if they were alkyl carbons. The method is applicable to alicyclic alkenes in small rings carbons are counted twice, i.e., from both sides of the double bond where applicable. The constant in the equation is the chemical shift for ethylene. The effect of other substituent groups is tabulated below. 

Tetraneopentyltitanium and ((CH2)2SiCH2)4Ti [33948-28-6] react with nitric oxide to yield compounds having R groups bonded ia two different ways, as shown by nmr (214). The reactions of NO with R TiCl and R2TiCl2 yield similar products that have Cl iastead of the —ONRNO substituent. 

Several types of nitrogen substituents occur in known dye stmetures. The most useful are the acid-substituted alkyl N-substituents such as sulfopropyl, which provide desirable solubiUty and adsorption characteristics for practical cyanine and merocyanine sensitizers. Patents in this area are numerous. Other types of substituents include N-aryl groups, heterocycHc substituents, and complexes of dye bases with metal ions (iridium, platinum, zinc, copper, nickel). Heteroatom substituents directly bonded to nitrogen (N—O, N—NR2, N—OR) provide photochemically reactive dyes. 

When an exocycllc function has a higher priority, it may be necessary to name a cationic heterocyclic substituent group. The most important case is that in which the heterocyclic substituent is bonded through its cationic center. Such cases may be named in two ways, as in (182) and (183). The simplest is to use the suffix -io , as used for the H3N— substituent, ammonio terminal e is elided. More generally, however, an -yl suffix is appended after -I um , as shown in the second names given for the examples. This method applies equally well to situations with other sites of attachment, and also allows one to name divalent substituents, e.g. (184) and (185). 

There are two stereochemically distinct possibilities for the conrotatory process. A substituent group might move toward or away from the breaking bond ... 

The radical stabilization provided by various functional groups results in reduced bond dissociation energies for bonds to the stabilized radical center. Some bond dissociation energy values are given in Table 12.6. As an example of the effect of substituents on bond dissociation energies, it can be seen that the primary C—H bonds in acetonitrile (86 kcal/mol) and acetone (92kcal/mol) are significantly weaker than a primaiy C—H... 

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