Covalent bond sigma

Transfer of a proton to an unsaturated carbon atom occurs more readily because 7r-electron pairs are available to form a new covalent (sigma) bond. A protonated alkene may undergo addition of a nucleophile in the second step, viz. 

Items 2 and 3 arise from the fact that both the "counterion" and the medium itself can markedly affect the nature of the growing chain end. Thus, the growing chain end may assume various forms that depend on the extent of electrical charge separation and range all the way from a polarized covalent (sigma) bond to a completely dissociated state of free ions. This characteristic presents the greatest distinction between the mechanisms of free-radical and ionic polymerization. 

The carbon atoms of many of the molecules that we have considered so far have used their four valence electrons to form four single covalent (sigma) bonds to four other atoms. We find, however, that many important organic compounds exist in which carbon atoms share more than two electrons with another atom. In molecules of these compounds some bonds that are formed are multiple covalent bonds. When two carbon atoms share two pairs of electrons, for example, the result is a carbon—carbon double bond ... 

In p-block elements, a central-atom lone pair is visualized as the limit of bonding to a ligand of lowest possible electronegativity, and thus acquires high s character. In d-block elements, a central-atom lone pair is of essentially pure d character (except for the special n(h) hybrid of ML2 coordination) and s character is essentially reserved for the covalent sigma skeletal bonds. 

In ethylene, there are two types of bonds. Sigma (tr) bonds have the overlap of the orbitals on a line between the two atoms involved in the covalent bond. In ethylene, the C-H bonds and one of the C-C bonds are sigma bonds. Pi (ir) bonds have the overlap of orbitals above and below a line through the two nuclei of the atoms involved in the bond. A double bond is always composed of one sigma and one pi bond. A carbon-to-carbon triple bond results from the... 

A e-bond (sigma-bond) forms when the bonding pair of electrons are localized directly between the two bonding atonts. Since the electrons in a o-bond are as close as possible to the two sources of positive charge (the two nuclei), a o-boml has the lowest energy and is the most stable form of covalent bond. Thus o-bonds are strong. A o-bond is always the first type of covalent bond to be formed between any two atoms a single bond must be a c-bond. 

Alkanes, also called paraffins or aliphatic hydrocarbons, are hydrocarbons in which the C atoms are joined by single covalent bonds (sigma bonds) consisting of two shared electrons (see... 

A major group of organometallic compounds has carbon-metal covalent single bonds in which both the C and metal (or metalloid) atoms contribute one electron each to be shared in the bond (in contrast to ionic bonds, in which electrons are transferred between atoms). The bonds produced by this sharing arrangement are sigma-covalent bonds, in which the electron density is concentrated between the two nuclei. Since in all cases the more electronegative atom in this bond is carbon... 

Conjugated polymers differ mostly through the bonding, which is covalent. The chains are A - A - A like with a sigma bond between the basic... 

In alkanes or saturated hydrocarbons, each carbon atom forms four covalent bonds. These bonds are C —C and C — H sigma bonds. Sigma bonds are very strong, so for this reason, alkanes are also known as paraffins which means "inert". 

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