The find of ferrocene in the 1950s was a room access to the country of organometallic chemical science and this happening was followed by the synthesis of monolithic organometallic composites. Although the find was unexpected, the impact was tremendous. These composites were extensively used as industrial homogeneous accelerators and besides in organic synthesis where they supplied new synthesis paths to unachievable compounds.
Figure Structure of ferrocene
Historically, there was a argument sing the construction of ferrocene. The unordinary and alone belongingss of this compound were contradicted with the expected construction, the purpose that Pauson and Kealy want to synthesise by the reaction of cyclopentadienylmagnesiumbromide with FeCl3. It was so come into involvement of these three chemists: Geoffrey Wilkinson, Robert Burns Woodward and Emil O. Fisher. The name of “ ferrocene ” with the “ east northeast ” stoping connoting aromaticity, following the construction of benzine was deduced by Wilkinson and Woodward based on the unusual stableness, diamagnetic nature, individual C-H stretching in the IR part and nonionic character of the compound. The sandwich construction was subsequently confirmed by X-ray crystallography. The carbon-metal bond of the ferrocene construction was a new construct of p-bonding of a carbocyclic ring to a metal atom. Following the name of ferrocene, came the term “ metallocene ” , a major going of classical theoretical account of ligand coordination.
In this peculiar experiment, surveies have been done for the synthesis and the responsiveness of ferrocene. In inside informations, this experiment was divided into three subdivisions with their specific purpose. The first subdivision is to synthesize and sublimate ferrocene under inert atmosphere. The 2nd subdivision purposes to look into the redox behavior of ferrocene. The 3rd subdivision purposes to try a Friedel-Crafts acetylation to do a mixture of acetyl ferrocenes, every bit good as to divide and place the merchandises by column chromatography.
Figure Structure of ferrocene, monoacetyl ferrocene and 1,1′-diacetyl ferrocene severally
SYNTHESIS & A ; PURIFICATION OF FERROCENE
Potassium hydrated oxide ( KOH, 8g, good crushed ) was added to 1,2-dimethoxyethane ( 20cm3 ) and assorted good in a 2-necked, round-bottom flasks with a magnetic scaremonger under inert status ( N2 flow ) . Cyclopentadiene ( 1.8cm3, 0.021mol, monomer denseness 0.786 g cm-3 ) was so added easy against the N2 flow followed by a changeless stirring for 10 proceedingss. The reaction mixture was so added with solution of FeCl2 ( 2g, 0.01mol ) in DMSO ( 8cm3, dropwise, vigorous stirring ) which was prepared before. As the add-on completed, the reaction mixture continuously stirred for 30minutes, its N2 flow disconnected and so poured into a prepared slurry ( HCl ( aq ) , 30cm3, 6moldm-3 ) and ice ( 30g ) ) .The slurry mixture so stirred ( 15 proceedingss ) , filtered, washed with H2O ( 4 x10cm3 ) and air-dried. The rough ferrocene obtained was so transferred to a ticker glass, dried ( steam bath, 5 proceedingss ) , broke gently, allowed to chill ( 5 proceedingss ) , weighed and its visual aspect recorded. It was so purified by sublimation ( Silicon oil bath ) , collected, weighed, acquire its runing point scope determined and submitted. The purified ferrocene obtained appeared as xanthous solids ( 1.3501g, 71.5 % ) ; mp 161-165 0C, 760mmHg.
REDOX BEHAVIOUR OF FERROCENE
Provided Ferrocene ( 100mg ) dissolved in propanone ( 10cm3 ) organizing a yellowish-orange solution. Solution of FeCl3.6H2O ( 0.1g ) and H2O ( 5cm3 ) was made up and yellowish-orange solution was formed every bit good. One-half of the ferrocene solution ( 5cm3 ) was so assorted with the Fe ( III ) solution and dark bluish solution was attained. A little spatula of ascorbic acid was so added ( with agitating ) to the dark bluish solution obtained ( 2cm3 ) followed by methylene chloride ( CH2Cl2, merely plenty to organize discernible bed ) and the mixture was shaken good. Yellow suspension was foremost observed earlier two beds of solution obtained. The top bed is detected as ferrocene in the methylene chloride while the bottom bed is identified to be the acerb bed. Apart from these trials, the balance of acetonic ferrocene solution was added with few beads of dilute Ag nitrate ( AgNO3, aq ) and the solution ( ab initio yellow-orange ) turns dark blue.
ACETYLATION OF FERROCENE
Orthophosphoric acid ( 0.25cm3,85 % ) was added to a mixture of ferrocene ( 0.25g, 1.34mmol ) and acetic anhydride ( 5cm3, denseness 1.08gcm-3 ) dropwise with changeless stirring. The mixture was protected with freshly-made CaCl2 tubing, heated smartly ( H2O bath, 10 proceedingss ) and poured onto ice ( 20g ) until all the ice melted. Sodium hydrogen carbonate ( NaHCO3, solid ) was used to neutralize the reaction mixture before it was cooled in ice bath ( 30 proceedingss ) . The semi-sludgy mixture obtained was subsequently extracted with ethyl ethanoate, acquire its filtrated collected, isolated ( taking the organic bed ) , dried ( MgSO4 ) , filtered by gravitation filtration and undergoes rotary vaporization. The compound obtained was subsequently separated by column chromatography and identified utilizing the thin bed chromatography analysis ( 70: 30 ratio of 40-60 crude oil quintessence: ethyl ethanoate as development dissolver ) every bit good as the IR and 1H NMR spectroscopy. There are two constituents of acetylated ferrocene compound obtained, monoacetyl ferrocene and diacetyl ferrocene. The monoacetyl ferrocene appeared as dark xanthous solid ; mp 80 – 84 oC, 760mmHg ; Vmax/cm-1 ( solution cell, DCM ) 1667 ( C=O ) ; I?H ( 400MHz, DMSO ) 4.53 ( , T, H ) , 4.80 ( , T, H ) . The diacetyl ferrocene appeared as dark orange solids mp N/A ; Vmax/cm-1 ( solution cell, DCM ) 1667 ( C=O ) ) ; I?H ( 400MHz, DMSO ) 4.53 ( , T, H ) , 4.80 ( , T, H ) .
Result & A ; Discussion
Synthesis & A ; Purification of Ferrocene
Initially, white precipitate formed when the well-crushed K hydrated oxide, KOH, dissolve in methylene chloride, DCM. After the add-on of cyclopentadiene, the suspension somehow turns chocolate-brown ruddy. Meanwhile, the disintegration of Fe ( II ) Cl2. 4H2O in DMSO gives xanthous green solution. When both of them mixed, the solution turns soiled light-green brown suspension. Addition of HCl slurry neutralises extra KOH in the mixture and bluish solution with xanthous drifting precipitates was observed after the add-on measure. As ferrocene is indissoluble in H2O, the xanthous petroleum ferrocene was easy collected from the Hirsch funnel during the filtration utilizing H2O. The filtrate which obtained as dark bluish solution was tested with three heaped spatula of SnCl2 and two beds of xanthous solution were formed. This indicates an excess ferrocene left in the filtrate and they were subsequently brought to rotary vaporization to take the dissolver. The rough ferrocene obtained was subsequently assembled and sublimed. The sublimated ferrocene obtained as xanthous solid.
( For computation of output, delight refer appendices. )
Redox behavior of ferrocene
Chemical reaction with FeCl3:
Yellow- orange solution of ferrocene turned todark bluish bespeaking the Fe ( II ) of ferrocene has been oxidised to Fe ( III ) . Hence, with FeCl3, ferrocene is a cut downing agent.
Chemical reaction with ascorbic acid:
Here, the dark bluish solution obtained turned back to yellow-orange coloring material indicated that the Fe ( III ) has been reduced back to Fe ( II ) .
Chemical reaction with silver nitrate, AgNO3:
In this instance, the yellowish-orange solution turned to dark bluish demoing that ferrocene, which is Fe ( II ) has been oxidised to Fe ( III ) . Hence, with AgNO3, ferrocene Acts of the Apostless as cut downing agent.
The three oxidation-reduction trials indicate that ferrocene is a good reduction agent.
Acetylation of ferrocene
At the beginning of the acetylation procedure, dark brown solution was observed. When the reaction mixture so poured into ice and neutralised by Na hydrogen carbonate, NaHCO3, gas evolved and identified as CO2 gas. Formation of this gas somehow slows down the neutralization procedure and finally semi-solid i.e sludgy was obtained.
Meanwhile, for thin bed chromatography ( TLC ) analysis, 70:30 ratio of 40-60 crude oil quintessence: ethyl ethanoate was chosen as dissolver system for the reaction mixture because this combination gives the best separation. The Rf value calculated utilizing expression as followed.
Rf = Distance travel by compound/ distance travel by dissolver
( For studies of TLC analysis, delight refer appendices. )
Separation of acetylation merchandises
The column chromatography method was used to divide the mixture of ferrocene and acetyl ferrocene. In specific, the surface assimilation chromatography was applied as the compounds are impersonal. Separation started by utilizing non polar eluent ( 100 % 40-60 crude oil quintessence ) in order to convey down all the ferrocene as it is non-polar compound. As the non-polar crude oil quintessence moves through the silicon oxide gel adsorbent, the non-polar ferrocene moved with it and could be observed as a xanthous set traveling down the column. The acetyl ferrocene was left behind. Finally, the mutual opposition of the eluent used bit by bit increased with the add-on of ethyl ethanoate to do up mixture of crude oil quintessence and ethyl ethanoate as eluents. These polar eluents map to convey down the polar ethanoyl group ferrocene and could be observed as dark xanthous set traveling down the column. The diacetyl ferrocene is more polar than the monoacetyl ferrocene. Hence, it was merely moved after the less polar monoacetyl ferrocene moved and utilizing the more polar eluents ( combination of 70:30 ratio of crude oil quintessence and ethyl ethanoate ) . The diacetyl ferrocene moved as a dark orange set. These observations show that mutual opposition is the most of import factor in dividing the impersonal compounds.
Despite of all the interesting observations mentioned, merely little sum of monoacetyl ferrocene were obtained after the rotary vaporization which was merely plenty to do the IR and 1H NMR analysis while the diacetyl ferrocene does non hold a good 1H NMR spectrum as the sample was non plenty. This is the ground why
Mass of monoacetyl ferrocene obtained = 0.07g
Mass of diacetyl ferrocene obtained = 0.01g