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In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist between two different elements: for example, in a carbonyl group between a carbon atom and an oxygen atom ...
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 ...
Moreover, the multiple bonds of the elements with n=2 are much stronger than usual, because lone pair repulsion weakens their sigma bonding but not their pi bonding.) [2] An example is the rapid polymerization that occurs upon condensation of disulfur, the heavy analogue of O 2.
The sp 2-hybridized carbon atoms, which are at their energy minimum in planar graphite, must be bent to form the closed sphere or tube, which produces angle strain. The characteristic reaction of fullerenes is electrophilic addition at 6,6-double bonds, which reduces angle strain by changing sp 2-hybridized carbons into sp 3-hybridized
In 1 H NMR spectroscopy, the hydrogen bonded to the carbon adjacent to double bonds will give a δ H of 4.5–6.5 ppm. The double bond will also deshield the hydrogen attached to the carbons adjacent to sp 2 carbons, and this generates δ H =1.6–2. ppm peaks. [14] Cis/trans isomers are distinguishable due to different J-coupling effect.
The polarity of C=O bond also enhances the acidity of any adjacent C-H bonds. Due to the positive charge on carbon and the negative charge on oxygen, carbonyl groups are subject to additions and/or nucleophilic attacks. A variety of nucleophiles attack, breaking the carbon-oxygen double bond, and leading to addition-elimination reactions.
Unsaturated hydrocarbons, which have one or more double or triple bonds between carbon atoms. Those with one or more double bonds are called alkenes. Those with one double bond have the formula C n H 2n (assuming non-cyclic structures). [1]: 628 Those containing triple bonds are called alkyne. Those with one triple bond have the formula C n H ...
Number of isomers including stereoisomers [3] [5] Molecular Formula Name of straight chain Synonyms 1 1 1 CH 4: methane: methyl hydride; natural gas 2 1 1 C 2 H 6: ethane: dimethyl; ethyl hydride; methyl methane 3 1 1 C 3 H 8: propane: dimethyl methane; propyl hydride 4 2 2 C 4 H 10: n-butane: butyl hydride; methylethyl methane 5 3 3 C 5 H 12 ...