# Conversion of oxalic acid to malonic acid

The reagents I have used here are $\ce{LiAlH_4}$ which reduces the carboxylic groups into alcohol.Used $\ce{HIO_4}$ which breaks up the molecule into methanal. Then I applied Grignard reagent which consisted ethyl for the alkyl part.Then I tried to oxide the terminal carbon into $\ce{COOH}$ but could not find a suitable reagent.

What is a better approach and a method to solve this question.

• Arndt–Eistert, maybe? Aug 20 '18 at 9:02
• en.wikipedia.org/wiki/Arndt%E2%80%93Eistert_reaction Aug 20 '18 at 10:53
• I would be wary of using a multistep reaction to try to homologate only one carboxylic acid group of oxalic acid... maybe forming a monoester first would work. Aug 20 '18 at 12:35
• I would fully reduce to the diol and convert to the epoxide. Then, form the halohydrin and oxidize to $\alpha$-chloro acetic acid. Should be pretty straightforward after that. Going through the halohydrin would allow you to desymmetrize the starting material.
– Zhe
Aug 20 '18 at 14:01

The Arndt-Eistert procedure suggested above seems very applicable to this problem. To use it we need ethyl oxalyl chloride. This can be prepared in 2 steps from oxalic acid by first esterification to form diethyl oxalate procedure here then reaction with PCl5 to form ethyl oxalyl chloride procedure here. This can undergo the Arndt-Eistert mechanism here with excess diazomethane then either irradiation or treatment with silver oxide to give monoethyl malonate. Simple base hydrolysis then gives the required.

Assuming you want oxalic acid as the only source of carbon

$\ce{(COOH)2 ->[\Delta, -CO2] CO ->[Cl2] COCl2 }$

$\ce{(COOH)2 ->[LiAlH4; H3O+] (CH2OH)2 ->[H3O+,\Delta] CH3CHO }$

$\ce{CH3CHO ->[B:-] CHO-CH2- ->[COCl2, huge excess; H3O+] CHO-CH2-COOH ->[Ag2O] CH2(COOH)2 }$

The key here is to split target molecule into $\ce{C1}$ and $\ce{C2}$ fragments and then find a way to find a way to make enolizable $\ce{C2}$ compound from oxalic acid. There is more then one way to obtain phosgene, one I pointed here wouldn't work in a lab. AFAIK phosgene can be obtained by thermal decomposition of oxalyl chloride, but I couldn't find trustworthy looking reference with quick googling.

rearrangement of ethylene glycol might required rather harsh conditions.

..... That one was fun.

• By Arndt–Eistert any luck? Aug 21 '18 at 12:42
• @starunique2016 The common restriction in this type of problems is either to not use outer sources of carbon or not use other organic compounds. Besides, Arnds-Eistert isn't very common. For this reasons I do not consider Arnds-Eistert a valid step for this problem unless OP states otherwise by quoting exact wording of the problem. Aug 21 '18 at 21:02
• If i want by Arndt-Eistert only? Aug 22 '18 at 10:15
• That ethylene glycol one i have my doubts Aug 22 '18 at 10:16
• @user57048 Rearrangement or synthesis ? Rearrangement is referenced in literature, it is a variant of pinacol–pinacolone rearrangement. Aug 22 '18 at 11:11