Compounds Containing Double Bonds

Remember that lone pairs occupy more space than bonded pairs, so the lone pairs are always put in positions where they will be least crowded. 

If the Lewis formida for a tmlectde or im shows mly one lone pair. In Unear, trigonal planar, tetrahedral, or octahedral electronic geometry, all positions are equivalent, so it doesn t matter where we place the lone pair. In trigonal bipyramidal electronic geometry, place the lone pair in the equatorial position where it is least crowded, and put the bonded atoms in the other positions. 

In Chapter 7 we constructed Lewis formulas for some molecules and polyatomic ions that contain double and triple bonds. We have not yet considered bonding and shapes for such species. Let us consider ethylene (ethene), C2H4, as a specific example. Its Lewis formula is 

Each atom has three electron groups. The VSEPR theory tells us that each C atom is at 

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The Meerwein reaction is a valuable method for the arylation of alkenes because of the easy availability of cheap aromatic amines and compounds containing double bonds. A disadvantage is that the yield is often low (normally 20-50%, in exceptional cases reaching 80%, see Table 10-3). The reaction can be carried out in water if the alkene derivative is sufficiently soluble otherwise an organic co-solvent is necessary. Meerwein et al. (1939) used acetone, which is still the most popular solvent used today. The mechanistic function of acetone will be discussed later in this section. 

Compounds containing double-bonded silicon and germanium atoms are the nearest analogues of olefins, ketones and thioketones. However, most of them are very unstable and highly reactive species. 

A method for determining the constitution of organic compounds containing double bonds. 

Organotin compounds containing double-bonded tin atoms. 411... 

Only a few stable organometallic compounds containing double-bonded tin are known. Stannaimines are very reactive and can be scavenged in various ways. The sterically crowded groups of compound 82 confer to it some stability. Compound 82 decomposes slowly in solution below 0 °C, according to reaction 37. See also Table 8 and reaction 44241. 

The use of bulky organic groups permitted the isolation of several thermally stable compounds containing double bonds between arsenic, antimony, or bismuth.8 9 56 Examples of homonuclear dimetal compounds, that is, diarsenes,... 

The type of compounds containing double bond and showing geometrical isomerism includes those having C=C, C=N and N=N structures. 

Dipole moments of compounds containing double bonds 287... 

The aim of this review is to focus on the acidity and basicity as well as some aspects of hydrogen bonding of organic compounds containing double-bonded functional groups. 

Fig. 10. UV-absorption spectrum of a filamentous organic microstructure from Transvaal stromatolite (ca. 2200 MY). Beam diameter of the instrument was below 1 pm. Absorption shoulders at 280 nm and 26S nm were assigned to nitrogenous organic compounds containing double bonds (L. Nagy, 1978) 35)...

These simplified rules are sufficient to name the vast majority of coordination compounds, but other rules are needed in special cases. For example, organic compounds containing double bonds can frequently coordinate to metals in more than one way, so the bonding mode must be incorporated in the name of the complexes. This type of complex will be described in Section 21.5. 

Electrochemically generated cation radical 252 derived from the cyclic alkylphenyl selenide 251 can react via two parallel paths deprotonization with the formation of compounds containing double bonds in the selenium-bearing rings and homolytic cleavage of the C(sp3)-selenium bond, followed by dimerization and formation of a diselenide 253 with an extended ring (Scheme 38) <1987ZOB609>. 

Since the spectacular isolation of the first stable disilene by West, Fink, and Michl in 1981 [19] this field has enjoyed a surge of activity [3]. Yet, despite the many important discoveries that have been made, the study of compounds containing double bonds to silicon is still in its infancy. In particular, relatively little is known on the effect of substituents, especially heteroatom substituents, on the properties of disilenes as only aryl-, alkyl-, (Me3Si)2N-, and MeaSi-substituted disilenes have been isolated to date [3]. With experimental progress being relatively slow, ab initio calculations provide a reliable, fast and economical method to extend our knowledge on these novel compounds. 

The synthesis and reactivity of germanium compounds containing double bonds to Si, Ge, and Sn has been a very active area of research over the past decade and has been extensively and recently reviewed. Particularly striking... 

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