Covalent compounds single bond

Double bonds also occur in other covalent compounds. By considering each double bond to behave spatially as a single bond we are able to use Table 2.6 to determine the spatial configurations of such compounds. 

Note that these compounds are covalently bonded compounds containing only hydrogen and carbon. The differences in their strucmral formulas are apparent the alkanes have only single bonds in their structural formulas, while the alkenes have one (and only one) double bond in their structural formulas. There are different numbers of hydrogen atoms in the two analogous series. This difference is due to the octet rule that carbon must satisfy. Since one pair of carbon atoms shares a double bond, this fact reduces the number of electrons the carbons need (collectively) by two, so there are two fewer hydrogen atoms in the alkene than in the corresponding alkane. 

The bicyclic compound 8.17 also serves as a source of the five-membered ring 8.20 upon reduction with SbPhs. In contrast to the related S or Se systems, 8.11a and 8.11b, both Cl substituents are attached covalently to Te in 8.20. Reaction of 8.20 with an excess of AsFs in SO2 produces the eight-membered cyclic [Tc2S2N4] dication, which exhibits a Te-Te bond length of 2.88 A (cf. 2.70 A for a Te-Te single bond) and no transannular S S bonding J... 

Although the S—O bond lengths in sulphoxides and sulphones seem to indicate that these are covalent double bonds, the dipole moments of these compounds obtained by calculation or by experimental measurements support the semipolar single-bond character in these compounds, and they should be represented as S - O, with about 66% ionic character14,15. 

Carbon likes to form bonds so well with itself that it can form multiple bonds to satisfy its valence of four. When two carbon atoms are linked with a single bond and their other valencies (three each) are satisfied by hydrogens, the compound is ethane. When two carbons are linked by a double bond (two covalent bonds) and their other valencies (two each) are satisfied by hydrogens, the compound is ethylene. When two carbons are linked by a triple bond (three covalent bonds) and their other valencies (one each) are satisfied by hydrogens, the compound is acetylene. 

Covalent bonding is the sharing of one or more pairs of electrons by two atoms. The covalent bonds in a molecule a covalently bonded compound are represented by a dash. Each dash is a shared pair of electrons. These covalent bonds may be single bonds, one pair of shared electrons as in H-H double bonds, two shared pairs of electrons as in H2C=CH2 or triple bonds, three shared pairs of electrons, N=N . It is the same driving force to form a covalent bond as an ionic bond—completion of the atom s octet. In the case of the covalent bond, the sharing of electrons leads to both atom utilizing the electrons towards their octet. 

Covalent radii are calculated from half the interatomic distance between two singly bonded like atoms. For diatomic molecules such as F2, this is no problem, but for other elements, such as carbon, which do not have a diatomic molecule, an average value is calculated from a range of compounds that contain a C-C single bond. 

Sometimes a given set of atoms can covalently bond with each other in multiple ways to form a compound. This situation leads to something called resonance. Each of the possible bonded structures is called a resonance structure. The actual structure of the compound is a resonance hybrid, a sort of weighted average of all the resonance structures. For example, if two atoms are connected by a single bond in one resonance structure and the same two atoms are connected by a double bond in a second resonance structure, then in the resonance hybrid, those atoms are connected by a bond that is worth 1.5 bonds. A common example of resonance is found in ozone, 0, shown in Figure 5-7. 

Both the long C-C bond distance (1.50 A) and the very short Pt—C distances (2.0 A) indicate the strong interaction between the adsorbed molecule and the three platinum surface atoms. The covalent Pt—C distance would be 2.2 A. The shorter metal-carbon distances indicate multiple metal-carbon bonding that may be carbene or carbyne-like. Compounds with these types of bonds exhibit high reactivity in metathesis and in other addition reactions The carbon-carbon single bond distance indicates that the molecule is stretched as much as possible without breaking of this chemical bond. 

Elements in organic compounds are joined by covalent bonds, a sharing of electrons, and each element contributes one electron to the bond. The number of electrons necessary to complete the octet determines the number of electrons that must be contributed and shared by a different element in a bond. This analysis finally determines the number of bonds that each element may enter into with other elements. In a single bond two atoms share one parr of electrons and form a a bond. In a double bond they share two pairs of electrons and form a a bond and a tt bond. In a triple bond two atoms share three parrs of electrons and form a cr bond and two tt bonds. 

Atoms within a molecule move relative to one another hy rotation around single bonds. Such rotation of covalent bonds gives rise to different conformations of a compound. Each structure is called a conformer or conformational isomer. Generally, conformers rapidly interconvert at room temperature. 

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