CHEM 237 - Organic Chemistry Lab Final TAMU Already Graded A

CHEM 237 - Organic Chemistry Lab Final TAMU Already Graded A Separation by liquid-liquid extraction is based on a) compound's dielectric constant in 2 dif solvents b) # of theoretical plates in the separation c) use of phase transfer catalysts d) difference in boiling points of 2 liquids e) distribution of a compound between 2 immiscible phases e) Distribution of a compound between two immiscible phases. Preparative gas chromatography is often chosen over distillation as a means of separation because gas chromatography a) is relatively inexpensive b) does not require thermally stable compounds c) can separate some compounds with identical boiling points d) will allow large quantities of sample to be injected e) does not require that compounds be volatile to be separated c) Can separate some compounds with identical boiling points In the Phase Transfer Catalysis experiment (10), a general form of quaternary ammonium salt is R4N+X. The R4N+, where R is an alkyl chain, can be in both the aqueous (polar) and organic (nonpolar) phase because [choose as many as apply] I) R4N+ is a charged species that can dissolve in the aqueous pase II) R4N+ is a charged species that can dissolve in the organic phase III) R is a hydrocarbon chain that can dissolve in the aqueous phase IV) R is a hydrocarbon chain that can dissolve in the organic phase I) R4N+ is a charged species (polar) and charged species can dissolve in the aqueous phase. IV) R is a hydrocarbon chain (nonpolar) and hydrocarbon chains can dissolve in the organic phase. Like dissolves like. What be an undesirable property for a recrystallization solvent? The solvent would a) dissolve no impurities, even at high temperatures b) dissolve the product to be isolated at all temperatures c) dissolve the product to be isolated at high but not at low temps d) have a low freezing point e) be nontoxic b) dissolve the product at all temps Absorption of energy in the infrared spectrum produces changes in a) molecular vibes b) bond angles c) dipole moments d) bond length e) all e) all Gas chromatographs usually contain a column which is packed w/a solid support and a liquid stationary phase. Separation occurs when a) your sample moves by capillary action through the column and interacts with the stationary phase b) your sample is carried through the column by a low boiling solvent c) the carrier gas takes your sample through the column w/o separating d) the carrier gas carries your sample through the column, where it interacts with the stationary phase and the sample components are separated e) your sample was separated between the ether and water layer d) the carrier gas carries your sample through the column, where it interacts with the stationary phase and the sample components are separated Which of the following qualitative tests could be used to distinguish between limonene and eugenol? a) ferric chloride test b) iodoform test c) bromine test d) baeyer test e) silver nitrate test a) ferric chloride Which of the following alcohols undergoes dehydration reaction (E1) most rapidly? a) 2-methyl-2-butanol b) 2-pentanol c) 3-pentanol d) 1-pentanol e) none, all of these have formula C5H12O and undergo dehydration at the same rate a) 2-methyl-2-butanol You are given a DCM solution with compounds A, B, and C. First extract with 3N NaOH, only a salt of A is in the aqueous layer. Re-extract organic layer with 3N HCl, only C in organic layer. Compound A is probably a) hexane b) benzoic acid c) naphthalene d) sodium sulfate e) benzocaine b) benzoic acid Which is true of molecular mechanics? a) employs ab initio methods to calculate strain energies b) treats chemical bonds as mechanical springs c) doesn't follow Hooke's Law d) requires cray super computers to do simple calculations e) all b) treats chemical bonds as mechanical springs Which is NOT a requirement for prep gas chromatography? a) sample must be volatile b) sample must be dry c) sample must be thermally stable d) sample size must be less than 5 microliters e) all d) sample size must be less than 5 microliters Reaction of naphtholate anion and allyl bromide involved a catalyst (tri-n-butyl ammonium chloride). The catalyst carries a) the water soluble naphtholate anion into the organic phase b) the hydrophobic naphtholate anion into the aqueous phase c) the water soluble allyl bromide into the organic phase d) the hydrophobic allyl bromide into the aqueous phase a) the water soluble naphtholate anion into the organic phase In an SN1 solvolysis rxn such as the one in lab a) the rate of rxn is dependent on rate of addition of NaOH b) rate constant, k, would 2X if alkyl halide amount was 2X c) rxn rate accelerated by use of a more polar solvent d) rate constant would be 0 if rxn mixtures weren't stirred e) rate constant would be decreased if NaOH wasn't added to neutralize acid c) rxn rate accelerated by use of a more polar solvent Tertiary alcohols reacting with sodium hypochlorite (NaClO) yield a) ketones b) carboxylic acids c) aldehydes d) amides e) none e) none Spilled nitric acid/sulfuric acid on you. What do you do? Wash it with a) water and apply 0.6 M sodium thiosulfate solution b) water and apply 0.6 M potassium permanganate solution c) cold water and apply 0.6 M sodium bicarbonate solution d) 0.6 M sodium hydroxide solution e) 0.6 M boric acid c) cold water and apply 0.6 M sodium bicarbonate solution Why do you allow a hot recrystallizing solution to cool slowly? a) quickly forms large crystals, trapping impure solution b) quickly forms small crystals, adsorbing impurities c) quickly may induce undesirable reactions d) quickly causes impurities to oil out, making it impossible to crystallize e) statement is false, quick cooling is correct b) quickly forms small crystals, adsorbing impurities Butyl Butyrate, an ester, differs from p-dioxane, an ether, by showing strong infrared absorbance at a) 3500 1/cm b) 2950 1/cm c) 2250 1/cm d) 1745 1/cm e) 1212 1/cm d) 1745 1/cm Simple distillation is most effective in separating compounds with a) almost identical boiling points b) greatly different densities c) widely different boiling points