Why is sulphuric acid not used during the reaction of alcohols with ki?

\( \newcommand\) • • • • • • • Learning Objectives • Give two major types of reactions of alcohols. • Describe the result of the oxidation of a primary alcohol. • Describe the result of the oxidation of a secondary alcohol. Chemical reactions in alcohols occur mainly at the functional group, but some involve hydrogen atoms attached to the OH-bearing carbon atom or to an adjacent carbon atom. Of the three major kinds of alcohol reactions, which are summarized in Figure \(\PageIndex\): Reactions of Alcohols. Oxidation and dehydration of alcohols are considered here. A flow diagram of three possible reactions of an alcohol. The final products of the reactions are also shown at the end of the flow diagram. Dehydration As noted in Figure \(\PageIndex\), an alcohol undergoes dehydration in the presence of a catalyst to form an alkene and water. The reaction removes the OH group from the alcohol carbon atom and a hydrogen atom from an adjacent carbon atom in the same molecule: Structural formula of ethanol dehydrating under excess concentrated sulfuric acid at 180 degrees celsius. The products are ethylene and a side product of a water molecule. Under the proper conditions, it is possible for the dehydration to occur between two alcohol molecules. The entire OH group of one molecule and only the hydrogen atom of the OH group of the second molecule are removed. The two ethyl groups attached to an oxygen atom form an ether molecule. Two molecules of ethanol are dehydrated under con...

In the presence of sulphuric acid (H 2SO 4), KI produces HI Since is an oxidizing agent, it oxidizes HI (produced in the reaction to I 2). As a result, the reaction between alcohol and HI to produce alkyl iodide cannot occur. Therefore, sulphuric acid is not used during the reaction of alcohols with KI. Instead, a non-oxidizing acid such as H 3PO 4 is used.

KI and H 2 S O 4 In the presence of sulphuric add H 2 S O 4, K I produces H I The reaction is given below: 2 K I + H 2 S O 4 → 2 K H S O 4 + 2 H l Oxidising nature of H 2 S O 4 Since H 2 S O 4 is an oxidising agent, it oxidizes H I to l 2 . The reaction is given below: 2 H I + H 2 S O 4 → I 2 + S O 2 + 2 H 2 O Therefore, the reaction between alcohol and H l to produce alkyl iodide cannot occur. So, sulphuric acid is not used during the reaction of alcohols with K I . Instead, a non-oxidising acid such as H 3 P O 4 is used.

I suspect $\ce$ gives iodides in good yields. (1) Katritzky, A. R.; Ramsden, C.; Taylor, R. J. K. Carbon with One Heteroatom Attached by a Single Bond; Comprehensive Organic Functional Group Transformations II; Elsevier Science Ltd, 2004; Vol. 2. ISBN: 978-0-08-044253-2 $\begingroup$ @Jan Could you please provide a reference or more details on your reaction control? From what I remember (I might be mistaken though) reaction $\ce$, resulting in low yield of iodoalkane. $\endgroup$ The synthesis of alkyl halides from the corresponding aliphatic alcohols using concentrated hydrohalogen acids was investigated by Klein, Zhang and Jiang. [1] They note: [W]e found that the reflux of 1-butanol ($\pu$ reaction to proceed. I point to the other answers as to why using sulphuric acid instead of phosphoric acid is a bad idea in the case of hydrogen iodide. Thus, to sum up: • hydrogen iodide is sufficiently acidic to protonate the corresponding alcohol and drive the reaction. More acids are not needed. • hydrogen bromide is not acidic enough to drive the reaction. Adding sulphuric acid protonates the alcohol partially and allows the reaction to proceed. • in the case of weakly soluble alcohols and hydrogen iodide, phosphoric acid may be used instead since it does not oxidise iodide (while sulphuric acid does). [1]: S. M. Klein, C. Zhang, Y. L. Jiang, Tetrahedron Lett. 2008, 49, 2638–2641. DOI: First of all, this question is very interesting. Though it looks simple at first glance, it re...

In the presence of sulphuric acid (H 2SO 4), KI produces HI is an oxidizing agent, it oxidizes HI (produced in the reaction to I 2). As a result, the reaction between alcohol and HI to produce alkyl iodide cannot occur. Therefore, sulphuric acid is not used during the reaction of alcohols with KI. Instead, a non-oxidizing acid such as H 3PO 4 is used.