mattodd
commented
8 years ago Hi @doravont - welcome aboard! Could you take a quick look at some previous comments I wrote about this "hand-over" phase and see if there's anything we (as onlookers) could benefit from. I like the way that you're framing this Issue, i.e. as a question that can be closed. But remember not to orphan this issue if you can help it, e.g. by installing a link to this page in your lab notebook.
I would read this procedure as: chloroform is added to the aqueous layer that has previously been separated from the organic layer. But it's not a well-written procedure, since "extraction" normally implies something you want. Here I'd take this as meaning that unreacted S/M is removed from the aqueous phase, and the aqueous phase is then acidified.
MFernflower
Liana Alves ( @lianaboo3 ) and I will be taking over Steph Terrell and John Halifax's work on "The Ketone", and below is their most recent proposed scheme:
We have begun the first step based off of this paper: Collot, A.-G.; Courtney, M.; Coyne, D.; Eustace, S. E.; O’Ferrall, R. A. M. The Journal of Organic Chemistry J. Org. Chem. 2009, 74 (9), 3356–3369.
The experimental section we are following reads: Phenylethylacetate (5.49 g, 0.033 mol) and methyl pyrazinoate (4.0 g 0.027 mol) in dry THF (30 mL) were added dropwise with stirring to a freshly prepared solution of sodium ethoxide (0.75 g sodium, 0.033 mol) in 12 mL of ethanol. The solution turned orange and then dark red during the course of the addition. It was heated to reflux for 3 h and after cooling poured into water (200 mL). Unreacted starting material was extracted with chloroform and the solution acidified with concentrated sulfuric acid to give a brown semisolid which was extracted with chloroform (3 × 100 mL). The product was dried (Na2SO4) and evaporated to give a brown oil which solidified on standing (4.05 g, 60%). A portion of the product (2.5 g) was purified by flash chromatography on silica. Elution with 10:2 hexane/ethyl acetate gave 1.1 g of white solid.
We were hoping for some clarification regarding the italicized part, since it is a bit unclear as to which solution they are referring to. When we attempted these steps, we accidentally added both water and chloroform to an extraction funnel, followed by concentrated sulfuric acid. However, Rob Broadrup read it as doing the extraction of chloroform first to remove starting material in the organic layer, and then adding sulfuric acid to the remaining aqueous layer with product. Since we already had water, chloroform and acid in the extraction funnel, we went ahead and did the extraction and collected the organic layer, dried it with Na2SO4, and concentrated it under reduced pressure, yielding a dark brown liquid.
Our lab notebook can be found here: http://malaria.ourexperiment.org/ketone_q2