CHM 2211L Key PASSED Exam Questions and CORRECT Answers
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CHM 2211L
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CHM 2211L
Mixtures have (higher/lower) melting points than pure substanceslower
What is the purpose of sodium acetate solution in the amide synthesis of
acetophenetidin?In the acylation reaction, the amine acts as a nucleophile, but we have
the ammonium salt present in our solution. This ammonium salt c...
CHM 2211L Key PASSED Exam Questions and CORRECT Answers Mixtures have (higher/lower) melting points than pure substances ✔✔✔ lower What is the purpose of sodium acetate solution in the amide synthesis of acetophenetidin? ✔✔✔ In the acylation reaction, the amine acts as a nucleophile, but we have the ammonium salt present in our solution. This ammonium salt can't act as a nucleophile (it doesn't have non -bonded electrons to use), so we need to add something to deprotonate the ammonium salt. This is the purpose of the sodium acetate - it is just a weak base that can deprotonate the salt to free the amine so that it can participate in the acylation reaction Why did we use charcoal/hot gravity filtration? ✔✔✔ to remove "COLORED" insoluble impurities. If you use too much, you might remove your good reagents too, and your yield will be lower. Why use a stemless funnel in hot gravity filtration? ✔✔✔ We want to get the solution through the funnel as quickly as possible, and we don't want get stuck in the stem. If we used one with stem, it is most likely there will be crystals crystallize in the stem and stuck the funnel. Why do we keep the filtration hot during filtration? ✔✔✔ To keep our desired compound soluble during the filtration. Otherwise if it precipitates, it will get filtrated. Where is water coming in and coming out in the condenser during reflux? ✔✔✔ Water in from the bottom and water out from the top. To keep the condenser full of water. What kind of solvent do we need in recrystallization? ✔✔✔ (water) hot: desires is soluble, impurities soluble cold: desired insoluble , impurities soluble When we shake the separatory funnel while doing extraction, a emulsion might form. If that happens the best thing to do is __________? ✔✔✔ add some "brine" to make the layers separate well Stopper during an extraction must be ______ ✔✔✔ removed; otherwise there will be some vacuum in the funnel when we drain down some of the solutions, and if the vacuum is created, we can't drain more solution down. Extraction vs Washing ✔✔✔ Although the process is the same for both, the distinction is where the desired compound is located. When we are "extracting", we are removing the desired compound from a mixture such that the desired compound ends up in the aqueous phase (typically as an ion that will subsequently be neutralized). "Washing" leaves the desired compound in the organic phase while it removes other impurities to the aqueous phase. What is the major idea behind separating a mixture? ✔✔✔ The idea to separate the mixture is to choose a base that only react with one compound and does not react w ith the other. Make only one of them become a salt and that salt will be in aqueous solution and the other one remain unchanged and stays in organic solution. That is how we separate them. If you aim to separate a mixture of solids, you should get back two ________? ✔✔✔ solids; For the salt in aqueous solution, you need to add acid to protonate the salt and it may precipitate as a solid. For organic solution, add brine to remove most of the wa ter, then MgSO4 to remove the leftover water, then evaporate the solvent to get the solid. Electron Donating ✔✔✔ those with lone pairs Electron Withdrawing ✔✔✔ those without lone pairs Stationary phase ✔✔✔ silica paper (polar) Mobile Phase ✔✔✔ Solvent (hexane/ ethyl acetate mix) If a solvent is changed to become more polar, how will Rf values change? ✔✔✔ Polar compounds will move up further, making Rf values go up for polar compounds The disubstituted product is ✔✔✔ 1,1-diacetylferrocene, because the first carbony l group deactivate the first ring
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