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Photochemical Electrocyclic Reactions: Stereochemistry01:26

Photochemical Electrocyclic Reactions: Stereochemistry

The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
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Thermal and Photochemical Electrocyclic Reactions: Overview01:26

Thermal and Photochemical Electrocyclic Reactions: Overview

Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
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Extracorporeal Removal of Drugs: Peritoneal Dialysis and Hemodialysis01:30

Extracorporeal Removal of Drugs: Peritoneal Dialysis and Hemodialysis

Patients with end-stage renal disease (ESRD) or those experiencing drug overdose often require extracorporeal methods to eliminate accumulated drugs and metabolites. Hemoperfusion, hemofiltration, and dialysis are the primary techniques to rapidly remove harmful substances without disrupting the patient's fluid and electrolyte balance. For those with compromised renal function, dosage adjustments of concurrent medications may be necessary during extracorporeal drug removal.Dialysis is a process...
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Extracorporeal Removal of Drugs: Hemoperfusion and Hemofiltration01:25

Extracorporeal Removal of Drugs: Hemoperfusion and Hemofiltration

Hemoperfusion and hemofiltration are critical techniques in medical treatments to eliminate accumulated drugs, metabolites, and electrolytes from the bloodstream. These methods are particularly vital in cases of accidental poisoning and drug overdose.Hemoperfusion involves passing blood through an adsorbent material to remove unwanted substances. The main adsorbents used in hemoperfusion include activated charcoal and Amberlite resins. Activated charcoal can adsorb both polar and nonpolar...
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Extracorporeal Removal of Drugs: Continuous Renal Replacement Therapy01:26

Extracorporeal Removal of Drugs: Continuous Renal Replacement Therapy

Continuous Renal Replacement Therapy (CRRT) is an essential intervention for patients experiencing severe kidney dysfunction. This therapy offers a continuous mechanism for removing fluids and toxins from the bloodstream, leveraging the patient’s blood pressure to facilitate filtration through a specialized filter. This method contrasts with intermittent dialysis, providing a gentler and more consistent removal of waste products and excess fluid, which is particularly beneficial in...
163
Thermal Electrocyclic Reactions: Stereochemistry01:17

Thermal Electrocyclic Reactions: Stereochemistry

The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
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