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In fact, the carbon atoms in the single bond need not be of the same hybridization. Carbon atoms can also form double bonds in compounds called alkenes or triple bonds in compounds called alkynes. A double bond is formed with an sp 2-hybridized orbital and a p-orbital that is not involved in the hybridization. A triple bond is formed with an sp ...
Sp 2-hybridized carbon groups attached to tin are the most commonly used coupling partners, and sp 3-hybridized carbons require harsher conditions and terminal alkynes may be coupled via a C-H bond through the Sonogashira reaction. Relative rates of the Stille reaction
For this molecule, carbon sp 2 hybridises, because one π (pi) bond is required for the double bond between the carbons and only three σ bonds are formed per carbon atom. In sp 2 hybridisation the 2s orbital is mixed with only two of the three available 2p orbitals, usually denoted 2p x and 2p y. The third 2p orbital (2p z) remains unhybridised.
For example, the C−H bond length is 110.2 pm in ethane, 108.5 pm in ethylene and 106.1 pm in acetylene, with carbon hybridizations sp 3 (25% s), sp 2 (33% s) and sp (50% s) respectively. To determine the degree of hybridization of each bond one can utilize a hybridization parameter (λ).
The type of bonding can be explained in terms of orbital hybridisation. In ethylene each carbon atom has three sp 2 orbitals and one p-orbital. The three sp 2 orbitals lie in a plane with ~120° angles. The p-orbital is perpendicular to this plane. When the carbon atoms approach each other, two of the sp 2 orbitals overlap to form a sigma bond.
An important aspect of the valence bond theory is the condition of maximum overlap, which leads to the formation of the strongest possible bonds. This theory is used to explain the covalent bond formation in many molecules. sp 3 hybridization in methane forms four equivalent sigma bonds with tetrahedral geometry.
Linear organic molecules, such as acetylene (HC≡CH), are often described by invoking sp orbital hybridization for their carbon centers. Two sp orbitals. According to the VSEPR model (Valence Shell Electron Pair Repulsion model), linear geometry occurs at central atoms with two bonded atoms and zero or three lone pairs (AX 2 or AX 2 E 3) in ...
Linus Pauling explained the importance of orbital overlap in the molecular bond angles observed through experimentation; it is the basis for orbital hybridization. As s orbitals are spherical (and have no directionality) and p orbitals are oriented 90° to each other, a theory was needed to explain why molecules such as methane (CH 4 ) had ...