front 1 When is Fractional distillation used instead of simple distillation? Which method is more efficient? | back 1 When the boiling points of two compounds differ by less than 40 °C, they cannot be separated by simple distillation. Fractional distillation is more efficient |
front 2 What is the function of the glass beads packed in the fractionating column during fractional distillation? | back 2 They provide a larger surface area to perform a series of repeated distillations in the column for separation of compounds. |
front 3 Where should the bulb of the thermometer be placed during distillation? | back 3 Right below the side-arm of the distilling head. |
front 4 List 4 errors that can lead to incorrect melting points? | back 4
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front 5 Describe an ideal solvent for recrystallization of compound X? | back 5 -X is insoluble at room temperature but soluble at the solvent’s boiling point - The solvent must either completely dissolve all the impurities at all temperatures or it must not dissolve the impurities at all - The melting point of X is higher than the solvent’s boiling point. |
front 6 What is the purpose of using activated carbon during recrystallization? | back 6 Activated carbon is used to remove colored impurities because it can absorb the impurities on its surface and then can be left behind in the filter paper. |
front 7 If a student uses too much activated carbon, what can be the consequences? | back 7 Reduction of percent recovery since it can also absorb the compound to be purified. |
front 8 During recrystallization, what are some options if you see no crystal after cooling down the solution to room temperature? | back 8 -Cool in ice bath |
front 9 Indicate at 2 ways to visualize a TLC spot which is invisible under UV light. | back 9 Iodine Chamber or Stain (Dye) |
front 10 What is characteristic of compounds that travel far on TLC plates? | back 10 They are less polar |
front 11 What is characteristic of compounds that do not travel far on TLC plates? | back 11 They are more polar |
front 12 When reacting Br2 with Hexane, what is observed? | back 12 Solution remains red |
front 13 When reacting Br2 with Cyclohexene, what is observed? | back 13 Solution becomes colorless |
front 14 When reacting KMnO4 with Hexane, what is observed? | back 14 Solution remains purple |
front 15 When reacting KMnO4 with Cyclohexene, what is observed? | back 15 A dark brown or black precipitate is formed |
front 16 When reacting H2SO4 with Hexane, what is observed? | back 16 No heat is generated |
front 17 When reacting H2SO4 with Cyclohexene, what is observed? | back 17 Heat is generated |
front 18 In Gas Chromatography, how does Boiling point influence retention time? | back 18 Compounds with low boiling points have faster retention times |
front 19 In Gas Chromatography, how does polarity influence retention time? | back 19 More polar compounds have slower retention times |
front 20 Define Theoretical Plate | back 20 Each condensation and revaporization that occurs on a fractioning column is a theoretical plate |
front 21 What is the retention time trend for the following compounds: butane, diethyl ether, and butanol in a Carbowax (medium-high polarity) column? | back 21 Butanol > diethyl ether > butane |
front 22 What is the reaction rate order for the Lucas test? | back 22 3o>2o>1o |
front 23 What is the reaction rate order for the TCICA test? | back 23 2o>1o>3o (3o is unreactive) |
front 24 What is the Lucas reagent? | back 24 ZnCl2 in HCl and H2O |
front 25 What is formed in the TCICA reaction? | back 25 A Isocyanuric acid precipitate and a carbonyl group |
front 26 What are Derivatives? | back 26 Unknown alcohols can be reacted to give stable, crystalline compounds called derivatives |
front 27 Why are derivatives useful? | back 27 Stable, crystalline derivatives can be used to identify unknown alcohols by comparing their derivative melting point with literature values. |
front 28 What is the purpose of Trituration in the Grignard lab? | back 28 Trituration is grinding of the crude product using petroleum ether in order to remove Biphenyl. |
front 29 Why does the addition of sodium or potassium Iodide catalyze SN2 reactions of alkyl halides? | back 29 Because Iodide is both a good leaving group and a good nucleophile. |
front 30 Define Extraction | back 30 Selectively dissolves the desired compound into an appropriate solvent. The desired compound is in the extract |
front 31 Define Washing | back 31 Removes impurities by dissolving them in an appropriate solvent. The desired compound is left behind |
front 32 Alcohol ease of dehydration dehydration order | back 32 3o>2o>1o |
front 33 Why is a slow rate of heating necessary to obtain an accurate melting point? | back 33 -It will let the apparatus, capillary, and compound all reach the same temperature at the same time. -A slow rate of heating will spread heat evenly throughout the sample to reach an accurate mp |
front 34 What is the difference between evaporation and boiling? | back 34 -Evaporation occurs below the BP. -Boiling occurs when the pressure of evaporating gas equals the pressure of the surrounding gas |
front 35 Why should you not add boiling chips to an already hot liquid? | back 35 Boiling will be too vigorous and out of control |
front 36 Describe the recrystallization procedure. | back 36
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front 37 In a solution of acetanilide, p-toluic acid, and p-tert-butylmethyl ether, what can be extracted using NaHCO3? | back 37 p-toluic acid |
front 38 Define Eutectic Composition | back 38 Both compounds are in equilibrium with the liquid |
front 39 Define Eutectic temperature | back 39 Lowest possible melting point for a mixture of X and Y |
front 40 Why would you choose methanol over water for a recrystallization solvent? | back 40 The boiling point of methanol is lower |
front 41 In the Extraction lab, what is the purpose of heating up and cooling down the mixture before adding HCl? | back 41 It helps get rid of trace amounts of TBME which can prevent recrystallization |
front 42 Which law takes into account the mole fractions of the compounds? | back 42 Raoult's Law |
front 43 When 2 compounds are miscible, what law should be used to determine overall pressure? | back 43 Raoult's law |
front 44 When 2 compounds are immiscible, what law should be used to determine overall pressure? | back 44 Dalton's law |
front 45 Why is steam distillation used preferable to simple distillation for isolating natural product with a high boiling point? | back 45 It allows for distillation at lower temperatures which avoids decomposition of the product |
front 46 How should be characteristic of a solvent for gas chromatography? | back 46 The solvent should be more volatile than the compound of interest. |
front 47 What is the difference between steam distillation and codistillation? | back 47 -Simple distillation is for miscible liquids and does not involve water, while steam distillation is for immiscible liquids and uses water. -Steam distillation is a form of codistillation that uses water. |
front 48 What form of distillation is used for immiscible liquids? | back 48 Codistillation. Steam distillation is a type of codistillation. |
front 49 For extraction, which solvents are more dense than water? | back 49 Dichlorromethane |
front 50 For extraction, which solvents are less dense than water? | back 50 Hydrocarbons and ethers |
front 51 What solvents are typically used for Sn1? | back 51 Polar protic (MeOH, EtOH) |
front 52 What solvents are typically used for SN2 | back 52 Polar aprotic (Acetone, DMSO, DMF, MeCN) |
front 53 When removing impurities during the recrystallization lab, what are the consequences of not preheating the gravity filtration apparatus? | back 53 It may cause premature crystal formation on the filter paper. |
front 54 In the recrystallization lab, what are the consequences of adding too much boiling solvent? | back 54 It will inhibit crystal formation because there will be difficulty in forming the crystal lattice if solvent particles are getting in the way. |
front 55 What is the purpose of boiling chips? | back 55 Boiling chips facilitate a smooth boil, preventing boiling over and uneven bubbles. |