Final LAB Review - DR. SHAEFAR PDF

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DR. SHAEFAR...

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The 4 methods to purify ● Distillation ● Chromatography ● Extraction ● recrystallization

-Who has my compound: ● How to determine the purity of the compound? Check melting pts, if is greater than 2 C there is impurities present in the compound ● Mixture melting pt: mix an unknown compound with a known compound. If the compounds have the same range then they are identical. ● Eutectic point is where the ratio of 2 different compounds is , gives a sharp mp and causes the mixture to seem pure but is not. ○ Also it melts at the lowest temperature for any mixture of the compounds. ■ Melting point can be used for the identification of an substance as melting point of the substances are very sharp ■ Rapid heating does not affect the melting point or a broken glass ■ Melting point is a physical property ■ Melting point of a compound is the temperature at which the liquid and the solid states are at equilibrium ■ If the compound is impure, the melting point will be higher and broader ■ An exotic mixture has a sharp melting point -Recrystallization ● The compound must be soluble in solvents ● Organic material needs to be solid, no liquid ● There should no solute left ● Solvent have less boiling point than the melting point of a compound ● Small crystal form when hot solution colds ● A hot filtration is carried out to remove insoluble impurities ● In order to achieve a high recovery of pure solvent, the solute should be dissolved in a minimum amount of solvent when the solvent is near its boiling point ● If purification occurs the range should be narrow and upper high melting point ● We used Acetanilide -IR spectroscopy ● Size of the atom and bond strength affected the frequency of IR ● Ketones and aldehydes fall btw the range 1670-1830 ● Acetic acid and ethanol are different by the peak if 1700 ● -TLC ● Nonpolar move faster, up and have a high rf

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Polar move slow are down and have a small rf, have strong interaction with the stationary phase

-Gas Chromatography ● The area of the peak recorded on a gas chromatography is related to the relative amount of the compound ● The length of the column, the rate of the flow of the column gas,and the temp ● GC can be used as an quantitative tool for determining composition of a mixture ● GC may be user to separate compounds with limited thermal stability a ● GC can be separated compound with close boiling point if their functionally is different ● GC requires that compound have resonance polarity

-EXP `11

-Dehydration of Cyclohexanol

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The dehydration of cyclohexanol, the slowest step is dehydration, therefore the determining step

The most stable dihedral angle is 180 Degrees for the anti-conformation

-Extraction ● The extraction solvent should be volatile ● Should form be immiscible with the other solvent used ● Should have a different density than the other liquid ● Multiples extractions are more productive than one extraction ● Desired properties for liquid extraction: ○ It must dissolve the substance being extracted but most not dissolve to any appreciable extent in the solvent from which the desired substance is being extracted ○ It should not extract starting reagents or by products ○ It doesn't not irreversible transform the substance being extracted ○ It should be readily separated from the desired solute after extraction ● Eugenol is at the top layers ●

Eugenol salt at water as OH removes the phenol hydrogen

-Safety

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Before returning your bin of glassware to the stockroom , we are required to rinse the glassware with acetone to insure that all trace of water have been removed, insure that no trace of organic material is remaining in the flask,Insure that no unwanted reaction will occur the next time the glassware is used due to the pretense of contamination If u spill with sulfuric acid wash ur hands with cold water and apply 0.6 M sodium bicarbonate solution Volatile organic should be transferred with the hood

Steam distillation is used to isolate better separation of 2 compounds with different boiling points

An amine + HCl is ionic salt SN1 the solvents is the nucleophile, 1st reaction order, decrease in polarity slow down the reaction We can determine k without knowing the exact concentration of NaOH Oxidizing reagents NaOCl KMNO4 K2Cr2O7 CrO3 -Phase transfer ● NaOH was used to produce naphtholate anion ● The phase transfer is Benzyl-tri-n-butylammonium chloride ● Brine is saturated NaCl solution ● Allyl-2-naphthyl ether had the highest rf value ● It transports the reactants between phases ● Quaternary ammonium salt ● The Naphtholate anion act as a nucleophile and Allyl Bromide as a electrophile

● Simple distillation can be used for separation, purification and and based upon boiling point of 2 substances

One advantage of steam distillation is that it allows the distillation of water insoluble compound that possess a high boiling point

Oxidation of 2nd OH...