In this lab we will be using the Friedel Crafts procedure of acetylation of ferrocene. Ferrocene is an atom of Fe bounded by two aromatic rings. We will utilize some reagents that will do the ferrocene to add either one ethanoyl group group to an aromatic ring or add two acetyl groups to each of the aromatic rings. In order to find how good this procedure had worked we employed: IR spectra analysis, column chromatography, and a small TLC. This experiment is relevant in today’s extremely industrialised universe. By using many of the techniques we employ in this lab, a company can synthesise new types of stuffs or complexs that could revolutionise an industry.
When we react the ferrocene with phosphorous acid and acetic anhydride, we obtain many disparate merchandises. Not merely do we acquire acetylferrocene, but we besides get diacetylferrocene, some unreacted ferrocene reactant, and acetic acid every bit good. We will utilize thin bed chromatography ( TLC ) , column chromatography ( CG ) , and IR spectra analysis in order to find the what proportions of each of these compounds will be present in the concluding merchandise.
Both TLC and CG are first-class methods of mensurating the presence of a given substance. Both methods turn around a compounds mutual opposition. As one recalls, mutual opposition is a step of the electronegativity of a compound determined by their arrangement in the periodic chart. Specifically, in this lab we are speaking about the difference in mutual opposition between the atoms of O and C. Ferrocene is comparatively low to none in mutual opposition. Acetylferrocene, because of the carbonyl functional group, is more polar than the ferrocene. Furthermore, diacetylferrocene, because of the 2:1 ratio of the carbonyl groups over the acetylferrocene, is the most polar of the batch.
As stated above, both TLC and CG take advantage of mutual opposition. Both methods have an highly polar stationary stage; specifically, silicon oxide or aluminum oxide gel is used. Through this polar stationary stage, a nomadic liquid stage is passed. Now, one can believe of a polar stationary stage as a bully that delaies in the high school halls for his hooligan friends. His hooligan friends, hooley’s as I like to name them, ever remain back to speak him; the remainder of the normal pupil organic structure merely maintain walking and base on balls him. The thought here is: like-stays-with- like. Analogously, those compounds which are most similar to the stationary substrate will remain behind to “hang out”. In this instance, the more polar the compound is, so the more it will remain behind as the remainder of the merchandise moves frontward in its liquid nomadic stage. TLC works by capillary action, where the nomadic stage is drawn up the TLC home base and across a polar TLC home base. CG, on the other manus, plants by holding gravitation pull the liquid Mobile phase down a polar loaded column. The joyous admiration of TLC and CG, so, is that they are therefore able to divide each component contained in the merchandise.
Methods & Procedure
The process of for this lab may be found in the pre-lab note for this experiment contained in the appendix. I will merely note on the of import characteristics of the process. The sum of start stuff for this lab was ca. 10 g. The computation for this may besides be found in the pre-lab I foremost added acetic anhydride to ferrocene ( FC ) and so warmed to add in the H3PO4 accelerator. I observed a red-violet colour to this mix of reactants. I so did a TLC and noted that the bulk of the sample was non the original ferrocene start stuff. Please see the pre-lab for reproductions of the TLC home bases used in this lab. Besides see table 1.2 for Rf values.
As one can see, this petroleum’s Rf is half that of the start stuff. This indicates that a reaction has decidedly occurred. Next we performed an extraction on this sample with Methylene Chloride ( MeCl ) and Sodium Hydroxide ( OH- ) . Please see the pre-lab for a image of what the extraction looked like. Then we transferred the lower organic potion into another phial with a small Na sulphate for drying. Then we transferred this to a tarred phial and dried off the MeCl in a N watercourse. MeCl is a great dissolver because it evaporates easy ( bp. ca. 48*C ) . Furthermore, we used a nitrogen steam so that we could minimise the sum of wet in regular air from being reintroduced into the sample. This was our 2nd petroleum sample and we did a Tender loving care on it with FC start stuff. See Tables 1.1 and 1.2 for sum of petroleum sample obtained and the Rf values. We allowed this to dry over till following weekend; we so performed a CG on this sample.
We placed this petroleum into the CG and so added three nomadic dissolvers to it in order to divide the petroleum. We used Hexane ( non-polar ) , Ethyl Acetate ( average mutual opposition ) and Methanol ( Nice and polar ) . The sample flowed down the column and into separate tarred phials for each colored stuff. The first was bright yellow. The second was a deep reddish carbon monoxide
The 3rd was a dark violet. I placed each phial into the N2 watercourse for concentration and so re-weighed each sample, called F1, F2, F3, severally, once more. The consequences are presented in table 1.1 at the terminal of the following subdivision. After yet another category lab on this experiment, I tried to take 5 milligrams of each sample and topographic point it into K-Br for IR spectra. However, after waiting till the following period for the IR, barely any of the stuffs we present in each phial. This was rather incomprehensible. I did pull off to acquire melt-temps, but I was merely able to grate together plenty of the F2 for IR spectra. See the appendix for the consequences of the IR spectra and see table 1.3 for the thaw temp values.
I besides took a TLC on each one every bit good; the values are presented in table 1.2 at the terminal of the following subdivision.
Results & Observations
The consequences of this experiment are reasonably consecutive forward and are summarized in tabular arraies 1.1 through 1.3 in this subdivision..
From the first petroleum sample’s TLC that was taken, one can see that approximately half of the material nowadays is composed of acetylferrocene and diacetylferrocene. Thus we continued along in the process. The consequences of the CG, which was performed next separated the component merchandises plenty that more TLC’s were able top be taken. The consequences of these TLC Rf’s state us that our separation was reasonably successful. As one can see, F1 spot A’s Rf, we have at least 90% of FC in detached mixture. This is great. It means the extraction was a success. The F2 per centum difference is 2.7% . This means that over 97% of this stuff are so AFC. OUTSTANDING consequences. This was a success for, one of the really few in this lab; therefore, I am rather happy. The per centum difference for the DAFC, nevertheless, is rather dissatisfactory. Merely 30% of this mix is so DAFC. This is non that good of a separation. The grounds for this are interpretable though. I believe it is due to inaccurate CG technique. I did non wait for all of the AFC to complete fluxing out of the column before I placed the vial down to obtain the DAFC. Therefore, as the TLC shows, most of this stuff is non DAFC. I think from comparing Rf’s to the AFC TLC plates that it is likely AFC; this does so corroborate that its likely the AFC. Furthermore, it besides could be some acetic intoxicant every bit good. If this was a side-product formed. After all, acetic intoxicant is rather polar; therefore it would be one of the last merchandises out along with the DAFC.
The IR spectra for F2 show us that we have largely AFC formed. The extremum at the 1700 scope indicates that c=o bonds are present in this sample. AFC does so hold the carbonyl edge nowadays. Furthermore, since the size of the extremum indicated the sums of c=o bonds present, we would anticipate it to be a smaller extremum than a F3 IR for DAFC. But I do non hold an IR for F3 for comparing. However, it likely has a large extremum there in proportion to the F2 anyhow.A big extremum around the 2900 grade indicates the nowadays of a H bonded to an aromatic ring. Our IR spectra for F2 does so demo a extremum in this scope. So we conclude that this sample is acetylferrocene.
In amount, this lab was successful. It taught us how to right prove the truth of a synthesis reaction; specifically, the acetylation of ferrocene. Our consequences show us the accurately synthesized and separated out the ferrocene and acetylferrocene from the reaction. The separation of the diacetylferrocene was non every bit successful as the extraction of the other two, but an account for this seems superficially valid.