Alcohols haloform reaction

Efaloform Reaetion. Ethyl alcohol reacts with sodium hypochlorite to give chloroform [67-66-3] (haloform reaction). 

Our recent studies on effective bromination and oxidation using benzyltrimethylammonium tribromide (BTMA Br3), stable solid, are described. Those involve electrophilic bromination of aromatic compounds such as phenols, aromatic amines, aromatic ethers, acetanilides, arenes, and thiophene, a-bromination of arenes and acetophenones, and also bromo-addition to alkenes by the use of BTMA Br3. Furthermore, oxidation of alcohols, ethers, 1,4-benzenediols, hindered phenols, primary amines, hydrazo compounds, sulfides, and thiols, haloform reaction of methylketones, N-bromination of amides, Hofmann degradation of amides, and preparation of acylureas and carbamates by the use of BTMA Br3 are also presented. 

Methyl aryl ketones react with iodine in the presence of excess pyridine to give pyridinium salts. Cleavage of the salts is readily accomplished by heating with aqueous-alcoholic sodium hydroxide. Over-all yields of 60-83% are reported. This two-step procedure affords a method similar to the haloform reaction for degradation of certain methyl ketones to acids with one less carbon-atom. 

Sodium hypobromite and sodium hypoiodite solutions react in an analogous manner and yield bromoform (CHBrj) and iodoform (CHI,) respectively. The smooth production of the trihalomethanes by the use of the appropriate hypohalides is termed the haloform reaction. It is applicable to all compounds containing the —COCH3 group or which yield a substance containing this group by oxidation (e.gr., acetaldehyde from ethyl alcohol). Iodoform is a stable, crystalline, yellow solid, m.p. 119°, with a characteristic odour it is only sparingly soluble in water and hence will separate, even in very minute quantity, from an aqueous solution and can easUy be identified by m.p. and mixed m.p. determinations. 

Ketones, Aldehydes, and Alcohols. The well-known Baeyer-Villiger oxidation of ketones by Oxone (eq 2) has been exploited in a variety of reactions. This protocol has been used with KHSO5 for cleavage of a- and /3-dicarbonyl compounds to esters or acids (eqs 30 and 31). This process is sirr5>ler, cheaper, and milder than the commonly used haloform reaction. 

The cuprate-mediated reaction of l-phenoxy-(2i ,7)-octadiene with propylmag-nesium chloride leads to undeca-l,6-diene, which may be selectively oxidised at the terminal double bond in a Wacker oxidation. Further oxidation with sodium hypobromite (haloform reaction) and reduction with lithium aluminium hydride then lead to (5 )-decenol, which can be esterified with acetic anhydride. The alcohol and the acetate are then mixed corresponding to their ratio in the natural pheromone composition. [187]... 

The seventh item in Table 8.6 is the sodium salt of the enolate ion of acetone. When any methyl ketone (i.e., a ketone of the form R-CO-CHj) or any secondary alcohol that can be oxidized to a methyl ketone (i.e., an alcohol of the form R-CH(0H)CH3) is treated with excess sodium hypochlorite (or any hypohalite), the haloform reaction occurs, resulting in the loss of the methyl group as chloroform (trichloromethane, CHCh) (or any haloform) and the formation of the salt of the... 

Now let s draw the forward scheme. The starting alcohol is oxidized upon treatment with chromic acid (alternatively, PCC can be used for this step). The resulting ketone is then treated with molecular bromine (Br2) and sodium hydroxide, followed by aqueous acid, to give a carboxylic acid (via a haloform reaction). Finally, the carboxylic acid is treated with ethanol in the presence of an acid catalyst, giving the desired ester (via a Fischer esterification). 

Exercise 17-12 Trichloromethane (chloroform) at one time was synthesized commercially by the action of sodium hypochlorite on ethanol. Formulate the reactions that may reasonably be involved. What other types of alcohols may be expected to give haloforms with halogens and base ... 

Fluorinated alkenes are able to insert into weak C-H bonds of various compounds branched alkanes, haloforms. alcohols, ethers, aldehydes and their corresponding ketals. These reactions usually involve the use of UV irradiation or radical-initiation catalysts, such as peroxides or azobisisonitriles. Variable amounts of telomcric products are also formed. Under the influence of ) -irradiation ( °Co source), one-to-one adducts are obtained predominantly. Attack of the intermediate radical occurs preferentially on the less-hindered carbon of the fluorinated alkene. 

Depending on the catalyst system and the chosen reaction conditions, aliphatic and aromatic alcohols can in general act as substrates for oxidative carbonylations. In principle this reaction type can occur in the presence of metal ions which are able to oxidize CO in the presence of an alcohol function. As already mentioned above, it is also here necessary to carry out the reaction in the presence of a suitable reoxidant in order to establish a catalytic cycle process. Preferably that may be another metal salt, for example CuCU- Typical products and side products which are observed in the oxidative carbonylation of alcohols are alkyl and aryl carbonates, oxalates, formates, haloformates, acetals, and carbon dioxide. 

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