Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: Synthesis of Propylene Oxide (2-methyloxirane, 2-epoxypropane, etc.) via Chlorohydrin Intermediate

Posts: 21
Registered: 30-12-2022
Member Is Offline

[*] posted on 2-8-2023 at 11:54
Synthesis of Propylene Oxide (2-methyloxirane, 2-epoxypropane, etc.) via Chlorohydrin Intermediate

Hello my fellow chemists.

My ultimate goal here is to produce propylene oxide. I’ve read some patents (and used the search engine) and I have settled on one of two variations of the chlorohydrin process. I was hoping for some input or insights into potential pitfalls or improvements.

To those unfamiliar, the chlorohydrin-based synthesis of propylene oxide (methyloxirane, 1,2-epoxypropane, it is a compound of many names) is as follows:

chlo.png - 4kB

Epoxideringclosure.png - 5kB

Propene will be produced continuously via the acid catalyzed dehydration of 2-propanol with conc. sulfuric acid.

Now this can be performed continuously, forming hypochlorous acid (HClO) in situ, or batchwise by preforming the hypochlorous acid either via acidification of a solution of hypochlorite (Reaction 3), or by bubbling chlorine gas (Cl2) into an alkaline solution (Reaction 4). The problem with the latter process is the unavoidable formation of HCl which is subsequently neutralized to NaCl. This is problematic as the presence of chlorine anions drives the equilibrium of the following reaction to the left (Reaction 4):

NaClO- + H+ <-------> HClO + Na+


Cl2 + H2O <------> HClO + HCl


Additionally, the presence of chloride leads the the unwanted byproduct of 1,2-dichloropropane

The problem that is chloride anion presence has been resolved in a few ways in the literature, though I am only going to discuss one method. HClO can be extracted using methyl ethyl ketone, acetone, or ethyl acetate relatively efficiently, leaving the ionic salts behind in the aqueous phase. This solution can be stored for short periods (on the order of hours), though from the perspective of both safety and yield, it is highly recommended to use it immediately. Its use as an organic solution will be discussed later.

There are two practical possibilities to make hypochlorous acid. The first is to acidify commercial bleach (contains only NaClO and NaOH according to the SDS) with dilute sulfuric acid and extract it with acetone to use in a second reaction vessel. The second possibility is to acidify calcium hypochlorite Ca(ClO)2 with dilute sulfuric acid. The advantage of this option is that the insolubility of calcium sulfate means I could potentially avoid the solvent extraction and directly bubble propene into this solution. Or if I decide to use a secondary reaction vessel, I could simply filter off the precipitate and similarly avoid the solvent extraction. In all the outlined approaches, the pH is to be made 5.0 as this pH minimizes the amount of Cl2 and ClO- present and maximizes [HClO] (Figure 1).

UVVisHypochlorousAcid.png - 47kB

Figure 1

The chlorohydrin produced will be distilled and then dripped into calcium hydroxide solution to yield the epoxide. The worry here is that the hydroxide (or what) present can open the epoxide ring up to yield the diol. However, due to its low boiling point (~40C) it can be removed continuously as it forms with sufficient application of heat.

I've read a few patents on the matter (Attachment: chlorohydrinpatent.pdf (1MB)
This file has been downloaded 143 times) and haven't come across any method that exploits the insolubility of CaSO4. Was wondering if anybody had any insights into the topic?

Will be posting an update after attempting this later in the week.

[Edited on 2-8-2023 by SyntheticFunk]

[Edited on 2-8-2023 by SyntheticFunk]

[Edited on 2-8-2023 by SyntheticFunk]

[Edited on 2-8-2023 by SyntheticFunk]
View user's profile View All Posts By User

Posts: 29
Registered: 2-6-2023
Member Is Offline

[*] posted on 4-8-2023 at 07:40

I have also looked into a possible rout to ethylene oxide in the past. From what I can piece together in my notes it should be possible to synthesise it from 2-chloroethanol.
Only found one paper.
2-chloroethanol reacts in this reaction with a base such as NaOH.

Apparently 2-chloroethanol can be made by bubbling dry HCl into ethylene glycol (haven´t looked much into that part).

If this all is doable it would be a pretty good way to produce ethylene oxide.

Attachment: swain1959.pdf (842kB)
This file has been downloaded 142 times

View user's profile View All Posts By User

  Go To Top