UKY CHE 233 Final Exam Questions With Complete Solutions

Structure of 6,13-diphenylpentacene correct answer: 5 aromatic rings with 2 phenols attached at 6 and 13 What is the purpose of base in the aldol condensation reaction? correct answer: To react with an alpha hydrogen to form a nucleophile (the enolate anion) and as a catalyst Hexynide lithium reacts with 6,13-diphenylpentacene via.... correct answer: Nucleophilic addition to carbonyl What is the role of tin(II) chloride in the synthesis of pentacene derivative? correct answer: it reduces pentacene by adding electrons, creating an aromatic compound; acts as an indicator in lab (turns blue) Where do you dispose of salts made in the pentacene lab? correct answer: Hazardous Aqueous Liquid Acidic & Basic Chemical Waste What is the stationary phase in the column chromatographic purification of crude pentacene derivative? correct answer: Silicon dioxide The elimination step of the aldol condensation reaction is an example of: correct answer: E1CB True or false: Increasing the conjugation will decrease the energy of absorption. correct answer: True What are the major differences when looking at an IR spectra for 6,13-pentacenequinone and 6,13-diphenylpentacene? correct answer: 6,13-pentacenequinone: C=O bond (cm-1) 6,13-diphenylpentacene: CC triple bond (2250cm-1) What is LiHMDS? What is its purpose in this experiment? correct answer: Lithium hexamethyldisilazide LiHMDS= strong base, but not a nucleophile, will form a hexynyl anion Explain why LiHMDS is such a strong base relative to hydroxide ion. correct answer: Nitrongen is less electronegative than oxygen, TMS groups donate electron density to enhance effect The elimination of water during the aldol condensation is named (blank) typle of elimination. correct answer: dehydration (E1CB)