Chem 51LB Week Summer Session 1 Kevin Chen

Lecture and lab participation Dr. Borovik’s unique participation method… clapping

Lecture and lab participation Dr. Borovik’s unique participation method… clapping Who wants to get an A in this class?

Lecture and lab participation Dr. Borovik’s unique participation method… clapping Who wants to get an A in this class? Who will obey all safety rules in lab?

Lecture and lab participation Dr. Borovik’s unique participation method… clapping Who wants to get an A in this class? Who will obey all safety rules in lab? Who will write great lab reports and learn a lot and make me proud?

Experiment #5: Acid-catalyzed dehydration and base-catalyzed debromination Given: primary and secondary alcohol for acid- catalyzed dehydration and primary and secondary alkylbromides for base-catalyzed debromination (4 compounds total!) Goal: Setup and run reaction and use gas chromatography (GC) for anlaysis End game: identify stereo- and regio- chemistry of the reaction products, and compare E1 versus E2 Note : Make sure to get data from another group

Part A: acid-catalyzed dehyrdation Reactants: 1-butanol and 2-butanol Catalyst: concentrated sulfuric acid Products(s): 1-butene, trans-2-butene, cis-2- butene GC for analysis – Identification – Mixture(?) components aka product distribution

Part A: Setup Product is a gas! Sealed reaction vessel is DANGEROUS!

Gas Chromatography Separation technique of gaseous mixture based on differences in boiling points – Lower boiling point = more volatile = moves faster – Higher boiling point = less volatile = moves slower Two phases – Solid phase (really, really long capillary column) – Mobile phase (inert gas: helium or nitrogen) Similarity to TLC (based on polarity)

~0.1mm thin, and up to 100m long coiled inside an oven Can be packed

Separation technique comparisons Gas chromatographyLiquid chromatography (TLC) SampleGas and liquid (must vaporize) Liquid and solid (must dissolve) Separation is based on...Boiling pointPolarity Mobile phaseInert gasMixture of polar and nonpolar solvents (overall nonpolar) Stationary phaseLong copper columnSilica (polar) Separation methodTemperaturePolarity of mobile phase Can you use this to identify your compound? Yes! How?Compare to standards!

Separation technique comparisons Gas chromatographyLiquid chromatography SeparatesGas and liquid (must vaporize) Liquid and solid (must dissolve) Separation is based on...Boiling pointPolarity Mobile phaseInert gasMixture of polar and nonpolar solvents (overall nonpolar) Stationary phaseLong copper columnSilica (polar) Separation methodTemperaturePolarity of mobile phase Can you use this to identify your compound? Yes! How?Compare to standards!

Part 2: base-catalyzed debromination Reactants: 1-bromobutane and 2-bromobutane Catalyst: 1M tBuOK Products(s): 1-butene, trans-2-butene, cis-2- butene GC for analysis – Identification – Mixture(?) components aka product distribution

Looks familiar? It should! Note: need a water condenser

Experiment #6: Separation and identification of unknown mixture Given: mixture of unknown (2 compounds from 9 possible options) In lab goal: You decide! End game: separate the unknowns and identify them using ALL relevant spectroscopy data Note: Must research structures and properties before first lab! PENALTY… NO LAB!

Experiment #6: Separation and identification of unknown mixture Given: unknown mixture (2 compounds from 9 possible options) In lab goal: You decide! End game: separate the major component of the unknown mixture and identify BOTH unknowns using ALL relevant spectroscopy data Note: Must research structures and properties before first lab! PENALTY… NO LAB!

My game plan (before lab) RESEARCH! Only 9 possible compounds (but 72 different combinations) – Identify structures – Group them based on similarity Why is this useful? NMR! Properties – Are they Solid, liquid, or gas? Color? Why is this useful? Comparing physical property of pure, isolated sample – Are they acid, base, or neutral? Why is this useful? Acid/base extraction

Techniques at your disposal Melting point – mix melting point Thin layer chromatography – With standards (Rf) Recrystallization Acid/base separation NMR IR GC

My game plan (1 st lab) Identify unknowns – NMR – Perform simple experiments to confirm TLC and melting point Must develop a plan to separate mixture for 2 nd lab Start separation if possible (likely not)

Teaser for next week! Finish experiment #6 Practicals – Review next week in lecture