ЙОДИД (ХЛОРМЕТИЛ) ТРИФЕНИЛФОСФОНИЯ

Description

(Chloromethyl)triphenylphosphonium iodide is a phosphonium salt, a quaternary derivative of triphenylphosphine in which the phosphorus atom carries a positive charge and is bonded to three phenyl groups, a chloromethyl substituent and an iodine counterion. Salt serves as a stable storage form for chloromethyl ylide: deprotonation with a strong base converts it to phosphorane (chloromethylenetriphenylphosphorane), which undergoes a Wittig reaction with aldehydes and ketones, converting them to vinyl chlorides. This sequence is used as a method for one-carbon homologation of carbonyl compounds.

Basic Attributes

• CAS No.: 68089-86-1
• Chemical formula: C19H17ClIP
• English name: (Chloromethyl)triphenylphosphonium iodide
• Molecular weight: 438.67
• Exact weight: 437.98000
• BRN: 4062471
• DSSTox ID: DTXSID50466379
• PSA Features: 0
• XLogP3: 1.18080

Physico-chemical characteristics

The melting point is 210 °C with decomposition, which is typical for ionic phosphonium salts: when heated, the crystal lattice is destroyed before the true melting point of the neutral substance is reached. The zero value of the polar surface (PSA 0) in the calculation model is due to the ionic nature of the molecule - PSA prediction programs usually do not take into account charged fragments separately from the neutral framework. The XLogP3 distribution coefficient of 1.18080 indicates the moderate lipophilicity of the organic cation.

Scope of application

• precursor of Wittig's reagent - chloromethylenetriphenylphosphorane, for one-carbon homologation of aldehydes and ketones
• source of chloromethyl ylide in the synthesis of vinyl chlorides and subsequent aldehydes
• starting compound for the preparation of other phosphonium and phosphine derivatives
• reagent for laboratory organic synthesis, including the construction of fine chemical intermediates

Safety Information

• Hazard class code: 36/37/38 (irritating to eyes, respiratory system and skin)
• Safety instructions: 26 (in case of contact with eyes, rinse immediately with plenty of water), 36 (wear protective clothing)

Storage and transportation

Salt is stored in an airtight container in a cool, dry room, protected from direct sunlight, since phosphonium iodides can slowly oxidize and lose iodide ion. The container is kept separate from strong bases, which are capable of deprotonating the compound and converting it into a reactive ylide already in the warehouse. When working, use protective glasses and gloves in accordance with the specified hazard codes.

Practical features of work

As an ionic compound, the salt is highly soluble in polar aprotic solvents - dimethyl sulfoxide, dimethylformamide, acetonitrile, but is poorly soluble in non-polar hydrocarbons. To obtain a reactive ylide, the salt is treated with a strong base (sodium hydride, butyllithium or potassium alkoxide) at reduced temperature in an anhydrous solvent; the resulting chloromethylenetriphenylphosphorane is then reacted with the carbonyl substrate without isolation, since it is unstable in air. The iodide ion as a counterion makes the salt more soluble in organic media compared to its chloride or bromide analogs, which makes it easier to carry out the reaction under homogeneous conditions.

Related compounds

Phosphonium salt is considered on a par with bromide and chloride analogs (chloromethyltriphenylphosphonium bromide and chloride), which are used for the same transformations, but differ in solubility and production cost. The deprotonation product, chloromethyltriphenylphosphorane, is structurally identical to the neutral ylide obtained by other methods, making the salt a convenient laboratory source of the chloromethyl moiety for the Wittig reaction.