What is "double bond"

Bond \Bond\ (b[o^]nd), n. [The same word as band. Cf. Band, Bend.]

1. That which binds, ties, fastens, or confines, or by which anything is fastened or bound, as a cord, chain, etc.; a band; a ligament; a shackle or a manacle.

   Gnawing with my teeth my bonds in sunder, I gained my freedom.
   --Shak.

2. pl. The state of being bound; imprisonment; captivity, restraint. ``This man doeth nothing worthy of death or of bonds.''
   --Acts xxvi.

3. A binding force or influence; a cause of union; a uniting tie; as, the bonds of fellowship.

   A people with whom I have no tie but the common bond of mankind.
   --Burke.

4. Moral or political duty or obligation.

   I love your majesty According to my bond, nor more nor less.
   --Shak.

5. (Law) A writing under seal, by which a person binds himself, his heirs, executors, and administrators, to pay a certain sum on or before a future day appointed. This is a single bond. But usually a condition is added, that, if the obligor shall do a certain act, appear at a certain place, conform to certain rules, faithfully perform certain duties, or pay a certain sum of money, on or before a time specified, the obligation shall be void; otherwise it shall remain in full force. If the condition is not performed, the bond becomes forfeited, and the obligor and his heirs are liable to the payment of the whole sum.
   --Bouvier.
   --Wharton.

6. A financial instrument (of the nature of the ordinary legal bond) made by a government or a corporation for purpose of borrowing money; a written promise to pay a specific sum of money on or before a specified day, given in return for a sum of money; as, a government, city, or railway bond.

7. The state of goods placed in a bonded warehouse till the duties are paid; as, merchandise in bond.

8. (Arch.) The union or tie of the several stones or bricks forming a wall. The bricks may be arranged for this purpose in several different ways, as in English bond or block bond (Fig. 1), where one course consists of bricks with their ends toward the face of the wall, called headers, and the next course of bricks with their lengths parallel to the face of the wall, called stretchers; Flemish bond (Fig.2), where each course consists of headers and stretchers alternately, so laid as always to break joints; Cross bond, which differs from the English by the change of the second stretcher line so that its joints come in the middle of the first, and the same position of stretchers comes back every fifth line; Combined cross and English bond, where the inner part of the wall is laid in the one method, the outer in the other.

9. (Chem.) A unit of chemical attraction between atoms; as, oxygen has two bonds of affinity. Also called chemical bond. It is often represented in graphic formul[ae] by a short line or dash. See Diagram of Benzene nucleus, and Valence. Several types of bond are distinguished by chemists, as double bond, triple bond, covalent bond, hydrogen bond.

10. (Elec.) A heavy copper wire or rod connecting adjacent rails of an electric railway track when used as a part of the electric circuit.

11. League; association; confederacy. [South Africa]

    The Africander Bond, a league or association appealing to African, but practically to Boer, patriotism.
    --James Bryce.

    Arbitration bond. See under Arbitration.

    Bond creditor (Law), a creditor whose debt is secured by a bond.
    --Blackstone.

    covalent bond, an attractive force between two atoms of a molecule generated by the merging of an electron orbital of each atom into a combined orbital in the molecule. Such bonds vary in strength, but in molecules of substances typically encountered in human experience (as, water or alcohol) they are sufficiently strong to persist and maintain the identity and integrity of the molecule over appreciable periods of time. Each such bond satisfies one unit of valence for each of the atoms thus bonded. Contrasted with hydrogen bond, which is weaker and does not satisfy the valence of either atom involved.

    double bond, triple bond, a covalent bond which involves the merging of orbitals of two (or three) electrons on each of the two connected atoms, thus satisfying two (or three) units of valence on each of the bonded atoms. When two carbon atoms are thus bonded, the bond (and the compound) are said to be unsaturated.

    Bond debt (Law), a debt contracted under the obligation of a bond.
    --Burrows.

    hydrogen bond, a non-covalent bond between hydrogen and another atom, usually oxygen or nitrogen. It does not involve the sharing of electrons between the bonded atoms, and therefore does not satisfy the valence of either atom. Hydrogen bonds are weak (ca. 5 kcal/mol) and may be frequently broken and reformed in solution at room temperature.

    Bond of a slate or lap of a slate, the distance between the top of one slate and the bottom or drip of the second slate above, i. e., the space which is covered with three thicknesses; also, the distance between the nail of the under slate and the lower edge of the upper slate.

    Bond timber, timber worked into a wall to tie or strengthen it longitudinally.

    Syn: Chains; fetters; captivity; imprisonment.

n. (context chemistry English) A covalent bond in which two electron pairs (instead of the usual one) are shared between two atoms; most common between carbon atoms and carbon, oxygen or nitrogen atoms, but several other forms are known.

n. a covalent bond in which two pairs of electrons are shared between two atoms

A double bond in chemistry is a chemical bond between two chemical elements involving four bonding electrons instead of the usual two. The most common double bond, that is between two carbon atoms, can be found in alkenes. Many types of double bonds exist between two different elements. For example, in a carbonyl group with a carbon atom and an oxygen atom. Other common double bonds are found in azo compounds (N=N), imines (C=N) and sulfoxides (S=O). In skeletal formula the double bond is drawn as two parallel lines (=) between the two connected atoms; typographically, the equals sign is used for this. Double bonds were first introduced in chemical notation by prominent Russian chemist Alexander Butlerov.

Double bonds involving carbon are stronger than single bonds and are also shorter. The bond order is two. Double bonds are also electron-rich, which makes them reactive.

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Chemical compounds with double bonds

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Ethene structural.svg

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Ethylene

Carbon-carbon

double bond