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Topic: Help identifying reagents in a synthesis  (Read 2478 times)

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Offline Albacoide

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Help identifying reagents in a synthesis
« on: December 28, 2015, 04:10:09 PM »
Hello, for a given procedure, I'm trying to correctly identify which are the reagents and write a correct balanced equation.

Procedure

To a solution of 2’,3’-di-O-acetyl-5’-deoxy-5-fluoro-N4-(pentyloxycarbonyl)cytidine (2,5)g in CH2Cl2 (17ml) was added dropwise 1N NaOH (17ml) with stirring and cooling with ice bath. After stirring for 1 hour at 0 ºC, MeOH (0,9 ml) was added to the mixture and pH of the reaction mixture was adjusted to 6 by the addition of concentrated HCl and partitioned. The aqueous layer was extracted with mixed solvent of CH2Cl2/MeOH (95/5) successively (40 ml x 10). The combined organic layers were dried over anhydrous sodium sulfate and filtered. The solution was evaporated, and the residue was crystallized from ethyl acetate to give 5’-deoxy-5-fluoro-N4-(pentyloxycarbonyl)cytidine as colorless crystals

I believe NaOH is a reagent, and it's responsible for the removal of the Ac groups. Is this correct? Is MeOH also a reagent? What's the function of HCl?

Is the attached equation correct for this process?

Sorry if these questions are too basic. Thanks in advance.

Offline phth

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Re: Help identifying reagents in a synthesis
« Reply #1 on: December 28, 2015, 04:36:00 PM »
using methanol as a partitioning solvent mixture just seems bad.  It will create an emulsion which is a pain to separate.  DCM/HCl(aq) will work fine.  Correct, NaOH a reagent used for saponification of ester groups.  Sodium sulfate will absorb 10 waters to 1, so it's not really considered a reagent. The use of methanol seems kinda funky to me.  The only reason I could see it being used is to have the acid penetrate into the organic phase.  But again it seems like a non sequitur.  to balanace the equation convert all of tne reagents into moles and then equivalents

Offline Babcock_Hall

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Re: Help identifying reagents in a synthesis
« Reply #2 on: December 28, 2015, 08:16:46 PM »
If you left out the HCl, would the molecule be neutral or charged?

Offline Albacoide

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Re: Help identifying reagents in a synthesis
« Reply #3 on: December 28, 2015, 08:51:51 PM »
Thank you phth and Babcock_Hall.

I have another question.

I assume 2 moles of NaOH are needed to react with 1 mol of 2’,3’-di-O-acetyl-5’-deoxy-5-fluoro-N4-(pentyloxycarbonyl)cytidine, as there are two Ac groups to be removed.

Is this correct?


Offline phth

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Re: Help identifying reagents in a synthesis
« Reply #4 on: December 29, 2015, 02:00:48 AM »
Yes for every 1 mole of starting material, you need at least 2 moles of sodium hydroxide.

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