Covalent bonding of carbon

The trouble is that this diagram makes the structure look like a flat layer. The structure shown in Figure 2.3.3 is quite wrong. In fact, the four covalent bonds of carbon are arranged tetrahedrally around the carbon atom so that the actual structure is as shown by Figure 2.3.4. 

Often associated with the covalent bonding of carbon (as well other nomnetaUic substances) is the phenomenon of hybridization —the mixing (or combining) of two or more atomic orbitals with the result that more orbital overlap during bonding results. For example, consider the electron configuration of carbon Under some circum-... 

Carbon-oxygen and carbon-halogen bonds are polar covalent bonds and carbon bears a partial positive charge in alcohols ( " C—0 ) and in alkyl halides ( " C—X ) Alcohols and alkyl halides are polar molecules The dipole moments of methanol and chloromethane are very similar to each other and to water... 

The most important interatomic bond in polymers, and indeed in organic chemistry, is the covalent bond. This is formed by the sharing of one or more pairs of electrons between two atoms. An example is the bonding of carbon and hydrogen to form methane Figure 5.2). 

The polarity of covalent bonds between carbon and substituents is the basis of important structure-reactivity relationships in organic chemistry. The effects of polar bonds are generally considered to be transmitted in two ways. Successive polarization through bonds is called the inductive fect. It is expected that such an effect would diminish as the number of intervening bonds increases. 

Organic chemistry, then, is the study of carbon compounds. But why is carbon special Why, of the more than 30 million presently known chemical compounds, do more than 99% of them contain carbon The answers to these questions come from carbon s electronic structure and its consequent position in the periodic table (Figure 1.1). As a group 4A element, carbon can share four valence electrons and form four strong covalent bonds. Furthermore, carbon atoms can bond to one another, forming long chains and rings. Carbon, alone of all elements, is able to form an immense diversity of compounds, from the... 

Attached by a covalent bond to carbon atom 1 of the deoxyribose ring is an amine (and therefore a base), which may be adenine, A (22) guanine, G (23) cytosine, C (24) or thymine, T (25). In RNA, uracil, U (26), replaces thymine. The base bonds to carbon atom 1 of deoxyribose through the nitrogen of the —NH— group (printed in red) and the compound so formed is called a nucleoside. All nucleosides have a similar structure, which we can summarize as the shape shown in (27) the lens-shaped object represents the attached amine. 

The DNA monomers are each completed by a phosphate group, —O—P032, covalently bonded to carbon atom 5 of the ribose unit to give a compound called a nucleotide (28). Because there are four possible nucleoside monomers (one for each base), there are four possible nucleotides in each type of nucleic acid. 

Hydrogen and nitrogen are outer atoms, so they use atomic orbitals to form covalent bonds. The carbon atom has a steric number of 2, so it can be described using sp hybrids. With this information, we can construct the a bonding network for HCN ... 

A thiol contains an —SH group covalently bonded to carbon. Sulfur is just below oxygen in the periodic table, so a thiol is somewhat similar to an alcohol. Still, the chemical and physical properties of thiols differ significantly from those of alcohols. For example, whereas alcohols have inoffensive odors, thiols smell bad. The stench of skunk scent is due to thiols, including 3-methylbutanethiol. Thiols are important in proteins because of their abilities to form S—S linkages, which we describe in Section 13-1. 

These results strongly suggest that in coal structure the covalent bond of benzyl ethers composed of aliphatic carbon and oxygen will be entirely cleaved at temperatures lower than 400°C, and the covalent bond composed of aromatic carbon and oxygen will be considerably decomposed at 450°C, since the unit structure of bituminous coal is considered to be composed of polynucleus of several benzene rings. 

Fig. 4.8 Structure of graphite, pointing to 3D hexagonal unit and covalent bonds between carbon atoms, and van der Walls bonds between graphene planes and hydrogen...

The validity of reaction Scheme 1 is not limited to heterolyses of covalent bonds to carbon. It covers also cases where both X and Y are hetero-atoms (e.g. oxidation of halides and pseudohalides by OH, cf. Ref [40] or where X is a hetero atom and Y is a metal (cf. Ref [41])... 

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