Хлорметилтрифенилфосфоран

Description

Chloromethyltriphenylphosphorane belongs to the class of phosphoranes - neutral pentavalent derivatives of phosphorus with a formal ylide structure, in which the phosphorus atom bears three phenyl substituents and is linked to a chloromethylene group. The compound is a stabilized analogue of the Wittig reagent: replacing the hydrogen atom with a chlorine atom in the methylene moiety makes the ylide suitable for the conversion of aldehydes and ketones to vinyl chlorides using the classical Wittig reaction. Such vinyl chlorides are further hydrolyzed to aldehydes with a chain lengthened by one carbon atom, so the reagent is used as a means of one-carbon homologation of carbonyl compounds.

Basic Attributes

• CAS No: 57283-72-4
• Chemical formula: C19H18ClP
• English name: Chloromethyl Triphenylphosphine
• Molecular Weight: 312.77
• Exact weight: 312.77
• PSA Specifications: 13.59000
• XLogP3: 0.61430

Structure and reactivity

The phosphorus in the molecule is surrounded by three phenyl rings and a chloromethylene fragment, which gives the compound moderate polarity (polar surface area 13.59000 Ų) and lipophilicity corresponding to an XLogP3 value of 0.61430 - that is, the substance occupies an intermediate position between hydrophilic and lipophilic organophosphorus reagents. Like other triphenylphosphine derivatives, the compound is sensitive to moisture and atmospheric oxygen: during hydrolysis, the P=C bond is destroyed to form triphenylphosphine oxide and chloroacetaldehyde or its derivatives, therefore all operations with the reagent are carried out in an inert atmosphere and in anhydrous solvents.

Scope of application

• Wittig's reagent for the conversion of aldehydes and ketones to (1-vinyl chloride) derivatives
• intermediate in one-carbon homologation of aldehydes through the hydrolysis step of vinyl chloride
• starting compound for the preparation of phosphonium salts and other organophosphorus ligands
• laboratory reagent for fine organic synthesis, including the synthesis of fragments of natural compounds and pharmaceutical intermediates

Physical properties

The molecular mass of 312.77 g/mol coincides with the exact mass of 312.77, which is typical for organophosphorus compounds without isotopic labels. The polar surface area of ​​the molecule is small (PSA 13.59000 Ų), which reflects the predominance of non-polar aromatic moieties over the polar P=C center. The XLogP3 partition coefficient of 0.61430 indicates moderate solubility in both polar and non-polar organic solvents.

Storage and transportation

The reagent is stored in a sealed container under an inert gas (nitrogen or argon), in a cool, dry room, away from sources of moisture and strong oxidizing agents. When working with the substance, use skin and eye protection, since phosphoranes and their hydrolysis products can irritate mucous membranes. Transportation is carried out in accordance with the general requirements for organophosphorus reagents that are sensitive to moisture.

Practical features of work

When setting up the Wittig reaction, the reagent is usually introduced into the reaction mass at a low temperature in order to control the rate of formation of the oxaphosphetane intermediate and suppress side conversion pathways. The residue of tripheniphosphine oxide formed after the reaction is separated by chromatography or precipitation, since it is highly soluble in most organic solvents and requires additional purification of the target product. Compatibility with solvents is typical for organophosphorus ylides: the reagent is stable in toluene, tetrahydrofuran and diethyl ether, but decomposes in the presence of protic solvents - alcohols and water.

Related compounds

Chloromethyltriphenylphosphorane is considered on a par with other stabilized Wittig ylides - carbethoxymethylenetriphenylphosphorane and benzylidenetriphenylphosphorane, which differ in the substituent at the ylide carbon atom. The presence of a chlorine atom gives the compound a specific reactivity that is not available for purely hydrocarbon analogues: the resulting vinyl chloride can further undergo chlorine elimination or substitution reactions, which expands the synthetic possibilities compared to conventional homologation.