関: dissociation、dissociation reaction、dissociative disorder、fugue

WordNet

dissociative disorder in which a person forgets who they are and leaves home to creates a new life; during the fugue there is no memory of the former life; after recovering there is no memory for events during the dissociative state (同)psychogenic fugue
a dreamlike state of altered consciousness that may last for hours or days
a musical form consisting of a theme repeated a fifth above or a fourth below its first statement
a state in which some integrated part of a persons life becomes separated from the rest of the personality and functions independently (同)disassociation
(chemistry) the temporary or reversible process in which a molecule or ion is broken down into smaller molecules or ions
the act of removing from association
(mechanics) the equal and opposite force that is produced when any force is applied to a body; "every action has an equal and opposite reaction"
a response that reveals a persons feelings or attitude; "he was pleased by the audiences reaction to his performance"; "John feared his mothers reaction when she saw the broken lamp"
a bodily process occurring due to the effect of some antecedent stimulus or agent; "a bad reaction to the medicine"; "his responses have slowed with age" (同)response
doing something in opposition to another way of doing it that you dont like; "his style of painting was a reaction against cubism"
an idea evoked by some experience; "his reaction to the news was to start planning what to do"
extreme conservatism in political or social matters; "the forces of reaction carried the election"
tending to produce dissociation

PrepTutorEJDIC

フーガ,遁走(とんそう)曲
分離[作用];解離
{名}(…に対する)『反応』《+『to』+『名』》 / 〈U〉(…に対する)(政治的・社会的な)『反動』,逆コース《+『against』+『名』》 / 〈U〉〈C〉化学反応,化学変化 / 〈U〉〈C〉(物理学で)反作用

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/05/22 00:37:11」(JST)

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Dissociative substitution describes a pathway by which compounds interchange ligands. The term is typically applied to coordination and organometallic complexes, but resembles the Sn1 mechanism in organic chemistry. This pathway can be well described by the cis effect, or the labilization of CO ligands in the cis position. The opposite pathway is associative substitution, being analogous to Sn2 pathway. Intermediate pathways exist between the pure dissociative and pure associative pathways, these are called interchange mechanisms.^[1]^[2]

Complexes that undergo dissociative substitution are often coordinatively saturated and often have octahedral molecular geometry. The entropy of activation is characteristically positive for these reactions, which indicates that the disorder of the reacting system increases in the rate determining step.

Kinetics

Dissociative pathways are characterized by a rate determining step that involves release of a ligand from the coordination sphere of the metal undergoing substitution. The concentration of the substituting nucleophile has no influence on this rate, and an intermediate of reduced coordination number can be detected. The reaction can be described with k₁, k_-1 and k₂, which are the rate constants of their corresponding intermediate reaction steps:

Normally the rate determining step is the dissociation of L from the complex, and [L'] does not affect the rate of reaction, leading to the simple rate equation:

However, in some cases, the back reaction (k_-1) becomes important, and [L'] can exert an effect on the overall rate of reaction. The backward reaction k_-1 therefore competes with the second forward reaction (k₂), thus the fraction of intermediate (denoted as "Int") that can react with L' to form the product is given by the expression , which leads us to the overall rate equation:

When [L] is small and negligible, the above complex equation reduces to the simple rate equation that depends on k₁ and [L_nM-L] only.

Dissociative interchange pathway

Interchange pathways apply to substitution reactions where intermediates are not observed, which is more common than pure dissociative pathways. If the reaction rate is insensitive to the nature of the attacking nucleophile, the process is called dissociative interchange, abbreviated I_d. An illustrative process comes from the "anation" (reaction with an anion) of cobalt(III) complexes:^[3]

[Co(NH₃)₅(H₂O)]³⁺ + SCN⁻ {[Co(NH₃)₅(H₂O)], NCS}²⁺

{[Co(NH₃)₅(H₂O)], NCS}²⁺ [Co(NH₃)₅NCS]²⁺ + H₂O

Water exchange

The exchange between bulk and coordinated water is of fundamental interest as a measure of the intrinsic kinetic lability of metal ions. This rate is relevant to toxicity, catalysis, magnetic resonance imaging, and other effects. For octahedral mono- and dicationic aquo complexes, these exchange processes occur via an interchange pathway that has more or less dissociative character.^[4] Rates vary by a factor of 10¹⁸, [Ir(H₂O)₆]³⁺ being the slowest and [Na(H₂O)₆]⁺ being one of the fastest for octahedral complexes. Charge has a significant influence on these rates but non-electrostatic effects are also important.

Sn1CB mechanism

The rate for the hydrolysis of cobalt(III) ammine (NH₃-containing) halide complexes are deceptive, appearing to be associative but proceeding by a pathway that is dissociative in character. The hydrolysis of [Co(NH₃)₅Cl]²⁺ follows second order kinetics: the rate increases linearly with concentration of hydroxide as well as the starting complex. Studies show, however, that in the hydroxide deprotonates one NH₃ ligand to give the conjugate base of the starting complex, i.e., [Co(NH₃)₄(NH₂)Cl]⁺. In this monocation, the chloride spontaneously dissociates from this conjugate base of the starting complex. This pathway is called the Sn1CB mechanism.

References

^ Basolo, F.; Pearson, R. G. "Mechanisms of Inorganic Reactions." John Wiley: New York: 1967. ISBN 0-471-05545-X
^ R. G. Wilkins "Kinetics and Mechanism of Reactions of Transition Metal Complexes," 2nd Edition, VCH, Weinheim, 1991. ISBN 1-56081-125-0
^ G. L. Miessler and D. A. Tarr “Inorganic Chemistry” 3rd Ed, Pearson/Prentice Hall. ISBN 0-13-035471-6.
^ Helm, Lothar; Merbach, André E. (2005). "Inorganic and Bioinorganic Solvent Exchange Mechanisms". Chemical Reviews 105: 1923–1959. doi:10.1021/cr030726o.

UpToDate Contents

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1. 解離性健忘：疫学、病因、臨床症状、経過、および診断 dissociative amnesia epidemiology pathogenesis clinical manifestations course and diagnosis
2. 解離性同一性障害：疫学、病因、臨床症状、経過、評価、および診断 dissociative identity disorder epidemiology pathogenesis clinical manifestations course assessment and diagnosis
3. 心的外傷後ストレス障害の解離性：疫学、臨床症状、評価、および診断 dissociative aspects of posttraumatic stress disorder epidemiology clinical manifestations assessment and diagnosis
4. 離人症性・現実感喪失性障害：疫学、病因、臨床症状、経過、および診断 depersonalization derealization disorder epidemiology pathogenesis clinical manifestations course and diagnosis
5. QRS幅の広い頻脈の診断および治療のアプローチ approach to the diagnosis and treatment of wide qrs complex tachycardias

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