AskDefine | Define dissociate

Dictionary Definition



1 part; cease or break association with; "She disassociated herself from the organization when she found out the identity of the president" [syn: disassociate, divorce, disunite, disjoint]
2 regard as unconnected; "you must dissociate these two events!"; "decouple our foreign policy from ideology" [syn: decouple] [ant: associate]
3 to undergo a reversible or temporary breakdown of a molecule into simpler molecules or atoms; "acids dissociate to give hydrogen ions"

User Contributed Dictionary



  1. To make unrelated, to sever a connection, separate.
    A number of group members wish to dissociate themselves from the majority.
  2. In the context of "transitive|chemistry": To separate compounds into simpler component parts, usually by applying heat or through electrolysis.
    We dissociated the lead iodide into its elements by heating
  3. To part, to stop associating.
  4. In the context of "intransitive|chemistry}} To undergo dissociation.

Extensive Definition

Dissociation in chemistry and biochemistry is a general process in which ionic compounds (complexes, molecules, or salts) separate or split into smaller molecules, ions, or radicals, usually in a reversible manner. When a Bronsted-Lowry acid is put in water, a covalent bond between an electronegative atom and a hydrogen atom is broken by heterolytic fission, which gives a proton and a negative ion. Dissociation is the opposite of association and recombination. The process is frequently confused with ionization.

Dissociation constant

For reversible dissociations in a chemical equilibrium
AB \leftrightarrow A + B
the dissociation constant Kd is the ratio of dissociated to undissociated compound
K_d = \frac


The dissociation of salts by solvation in a solution like water means the separation of the anions and cations. The salt can be recovered by evaporation of the solvent. See also: Solubility equilibrium


The dissociation of acids in a solution means the split-off of a proton H+, see Acid-base reaction theories. This is an equilibrium process, meaning that dissociation and recombination takes place at the same time. The acid dissociation constant Ka is an indicator of the acid strength: stronger acids have a higher Ka value (and a lower pKa value).


Fragmentation of a molecule can take place by a process of heterolysis or homolysis


Receptors are proteins that bind small ligands. The dissociation constant Kd is used as indicator of the affinity of the ligand to the receptor. The higher the affinity of the ligand for the receptor the lower the Kd value (and the higher the pKd value).
dissociate in Bulgarian: Електролитна дисоциация
dissociate in Czech: Disociace molekul
dissociate in Danish: Dissociation
dissociate in German: Dissoziation (Chemie)
dissociate in Spanish: Disociación
dissociate in French: Dissociation (chimie)
dissociate in Italian: Dissociazione (chimica)
dissociate in Lithuanian: Disociacija
dissociate in Hungarian: Disszociáció
dissociate in Dutch: Dissociatie (scheikunde)
dissociate in Japanese: 解離 (化学)
dissociate in Polish: Dysocjacja elektrolityczna
dissociate in Slovak: Disociácia (chémia)
dissociate in Serbian: Електролитичка дисоцијација
dissociate in Finnish: Dissosiaatio (kemia)
dissociate in Swedish: Dissociation (kemi)
dissociate in Ukrainian: Електролітична дисоціація
dissociate in Chinese: 离解

Synonyms, Antonyms and Related Words

abrupt, abstract, alienate, cast off, cast out, catalyze, cut adrift, cut off, cut out, delete, depart, detach, dialyze, disarticulate, disassociate, disconnect, disengage, disjoin, disjoint, distance, disunite, divide, divorce, eject, electrolyze, estrange, expel, hydrolyze, isolate, leave, part, photolyze, pull away, pull back, pull out, segregate, separate, sequester, set apart, set aside, sever, shut off, split, stand aloof, stand apart, stand aside, step aside, subtract, throw off, throw out, uncouple, unyoke, withdraw
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