WHAT IS HALOFORM REACTION?

This type of reaction will start with the disproportionation of the halogen with the presence of the hydroxide ion.  In this, the reaction process will lead to the formation of halide or the hypo halite.   As a result of the reaction the hydroxide abstracts form the proton and the emulate.  The hypohalites react with any present methyl ketones, eventually forming a haloform. This reaction can also be assumed as an example of nucleophilic substitution reaction where the compounds can act as the nucleophile. There isthe chemical reaction that explained the process:

It can be observed that when there is a treatment of methyl ketone with the bromine halogen in aqueous sodium hydroxide solution there is an occurence of Polyhalogenation which is followed by the cleavage of the methyl group. As a result, it will lead to formation of the carboxylate and the tribromomethane which are the haloform produced during the process. This process was previously used to industrially produce chloroform, bromoform and iodoform.

The haloform reaction is considered as one of the oldest form of organic reactions.  This is one of the reaction is used for centuries and its history can be traced back to the year 1822 when Georges-Simon Serullas added potassium to a solution of Iodine in ethanol as well as that led to water resulting in the formation of potassium format and iodoform.

This kind of reaction is being used for qualitative analysis to indicate the presence of a methyl ketone. This kind of reaction also has some synthetic utility in the oxidative demethylation of methyl ketones if the other substituent on the carbonyl groups bears no enolizable α-protons. The products that are being formed during the reaction process are also being able to have new characteristics of its own and they are being widely used in other reactions as well.

HALOFORM REACTION MECHANISM:

The Haloform reaction will follow a definite mechanism Similar is the case of the Haloform reaction where there are three elaborate steps that will be followed , the steps are explained in brief  :

STEP 1

In this step, the base ice the hydroxide ion takes out the alpha hydrogen producing enolate.  Subsequently, in the reaction process that place between the enolate and the halogen that will lead to the formation of the halogenated ketone and that too with the halogens corresponding anion. In this process the bond gets broken and this will lead to the creation of the next levels of bond. The reaction will move on further and so there will be a sequence of events that will take place.

The figure below elaborated the process

STEP 2

In this step, the reaction will take place between the enolate and the halogen that will lead to the formation of the halogenated ketone along with the halogens that will relate to the corresponding anion that gets repeated twice. This results in the yielding of a tri-halogenated ketone.

The chemical reaction elaborated below can give the clear understanding of the same as well.

STEP 3:

In the third step,  the hydroxide ion present  that is present in the reaction acts as a nucleophile and then  attacks the electrophilic carbon which is doubly bonded to oxygen.  In the next process, the present carbon-oxygen double bond converts into a single bond thusmaking the oxygen atom anionic.   The chemical process will lead to thetransformation thatmakes it favorable for carbon oxygen double bonds to be formed. As a resultthe carbon attached to three halogens that are being displaced.  This reaction process will leave the compound carboxylic acid. In this the acid base reaction ensuesthat  the carboxylic acid donates a proton to the tri-halo methyl anion  thus helping in the formation of the haloform product.

 In the diagram below the process is being explained elaborately:

 In the final step 3, by following the step of halogenation we are able to lead the reaction to halogenation of a methyl ketone with excess halogen that will result in the formation of carboxylate ions and the haloform.  The main components that used in these reactions are methyl ketones, secondary alcohols etc…

HALOFORM REACTION EXAMPLE

This reaction will always require very simple ingredients.  The primary among them is the methyl ketone, a halogen in molecular form (i.e. Cl₂, Br₂, or I₂), and a base (usually some sort of metal hydroxide i.e. NaOH).  As the reaction process starts, the ‘R’ groupthat represents any general organic side chain and that it can be virtually denoted by anything. Here ‘X’ will represent the four halogens present in the group.