Seperate layers Container 1 - aq. Prep the elution sample mix of dyes and test tubes 2. Separation occurs in the column, based on the attraction to the column. The thermodynamically favored product was formed because sodium borohydride is not a sterically hindered reducing agent, and is therefore able to attack the 4- tert-butylcyclohexanone from the top face of the molecule despite the presence of the large tert-butyl group. Solvent started to boil 2.
Vapors reach cool condensing arm, condenses back to liquid 6. Never heat in a closed system. The solution - Hexanes in water are immiscibe. Melting point near the boiling point of the solvent A compound oils ut, impurities dissolve in the oil and impede recrystillization 14. Figure 1 below shows the structures of the metal hydride reducing agents. Structure: eliminate compounds containing H-bonds or dipole-dipole forces 2. Be sure that the absorbent is covered with solvent throughout 4 If the elution solvent flows through too slowly or is not polar enough to displace the desired compounds, poor reparation a elution dye mixture will appear to have nonhorizontal bands.
Alternatively, the melting point of both compounds could be measured on one apparatus to learn if they are likely to have the same identity without calibrating either melting-point apparatus. After identifying the peak at 3. Thin-layer chromatography indicated the presence of starting material in the reaction mixture, and thus, the reaction was stirred for an additional 30 minutes. Looking down carbon two-carbon one left and carbon one-carbon six right. Lithium aluminum hydride is similar to sodium borohydride in that it is not sterically hindered and has the ability to the attack the carbonyl from the top face. Each fraction wil lcontain a mixxture of dyes rather than isolated single dyes c very slow rate of the mobile phase - column was packed too much, bands will widen and coelute with each other.
L-Selectride is a bulky, sterically hindered reducing agent, and thus, does not have the ability to attack from the top face of the starting material. Due to the sp 2 hybridization of the carbonyl carbon, it is planar, and thus, can be attacked from either the top or bottom face of the molecule. The inert gas simply carries them down the column 1. The solute X is nice and organized at the bottom. In the other, the sample height is 4-5mm, and the mp range is found to be 141°-145. The mixture separates as a result of the equilibria between the mobile phase and stationary phase free state vs. Sample is vaporized in the heated chamber 3.
Water is polar has permanent dipoles and H-bonding, which is hardest to break. Poor separation can result because the lower part of one band may coeleute with the upperband 3 If the solvent level falls below the top of the absorbent, it can become dry and fall from the column. It will not interact as wiell with the stationary phase and result in a low retention time. The reported melting point range for the compound is 143°C. A mixed melting point experiment could be used to determine whether the two compounds have the same identity. Exotheric reactions between polar solvents and the absorbent can produce heat.
The product is a mixture of the cis and trans isomers as well as the starting material. Make sure you label collection flask 6. The enzyme reduction product exists as both R and S, and the chiral acid is strictly S configuration. Poor separation of components -- a. Easily to separate: Napthalene and Benzoic acid a. Lynn Bradley, The College of New Jersey. Placed below distilation head So the thermometer will accurately read the temp of the vapures about to distill 2.
N-butanol has a higher poiling point. Recover compounds by evaporating the elution solvents Sources of Confusion and common pitfalls in Column Chromotography 1. Consequently, these four protons create a quintet, and this is identified as the peak at 4. Being that the trans product is more thermodynamically stable, it is said to be under thermodynamic control. The ethyl acetoacetate contains both a ketone and an ester functional group. They did not fit well in the new crystal lattice. Thus, the hypothesis was correct.
A hot recrystallization solution should be filtered by gravity to avoid premature crystallization. Add Et2O diethyl ether - introduces the organic phase dissolvents both compounds 3. Thus, the L-selectride reduction of 4- tert-butylcyclohexanone is under kinetic control. Prepare silica slurry in hood, dry silica is an inhalation hazard 6. Collect layers in a labeled container Run bottom layer first : Container 1 - Aqeous layer with unwanted byproduct Container 2 - Organic layer with desired product 6. Understanding each metal hydride reducing agent allows for an educated guess as to whether the hydride will attack from the top or bottom face of the 4- tert-butylcyclohexanone. Conclusion The purpose of this experiment was to investigate the stereoselectivity of various hydride reducing agents.