Chem 241 - Study guides, Class notes & Summaries

What's the reason for filtration in recrystalization - correct answers to remove insoluble impurities ortho and para are more stable why - correct answers because allow for tertiary carbocation when can you skip filtration during recryst. - correct answers if no insoluble impurities are present why warm filter tip pipets - correct answers to prevent premature crystalization why cant the solvent from a recrystallization be removed via evaporation instead of centrifugation? - correct ...

Goals of Separation - correct answers recovery of product, purity of product Types of Chromatography - correct answers Adsorption - SP: solid, MP: gas/liquid Partitioning - SP: liquid, MP: gas/liquid Ion-Exchange - SP: bonded anion/cation, MP: liquid Molecular Exclusion - SP: has pores, MP: liquid Affinity - SP: antigen/antibody interactions, MP: liquid Electrophoretic - no SP Solvent Extractions based on - correct answers Some solvents are not miscible; "like dissolves like"; less ...

Van Deemter Equation - correct answers A-term: multiple paths - correct answers - only affects packed columns - A term goes down with uniformly packed columns - smaller SP particles decrease A - no A term in OT because there are no particles A term band broadening - correct answers different particles take different paths with varying lengths and times to get out of column B term: longitudinal diffusion - correct answers - smaller molecules diffuse more than larger molecules - incr...

What is a major safety concern for the griganrd lab - correct answers Et2O flammability What are two features of a good solvent - correct answers soluble at high temps, doesn't react with compound being purified Mixtures of two compounds will lead to what type of MP - correct answers lower and braoder ___________ solvents will dissolve the substance when hot, but not when cold - correct answers crystalization What leads to larger, purer crystals - correct answers slow cooling How...

Substituents on an aromatic ring can either increase or decrease the reactivity of the ring toward electrophiles. This effect is a result of the balance between - correct answers induction resonance Substituents may withdraw or donate electron density from/to the aromatic ring by induction, which depends on the ______ and/or ______ of the atom or group attached to the ring. - correct answers polarizability electronegativity Match each type of substituent to the correct inductive effect ...

What are the benefits of having smaller particles in HPLC? - correct answers high efficiency, higher plate number, higher pressure, shorter run time, better resolution due to uniform flow (reduced A-term, multiple pathway) what is plate height? - correct answers length of column required for 1 equilibration of solute between mobile and stationary phases What are the drawbacks of having smaller particles in HPLC? - correct answers lower detection limit, resistance to solvent flow, increased...

What was solvent-solvent extracted used for in experiment 1? - correct answers -to extract ethanol from alcoholic beverages (busch, busch light, and a non-alcoholic drink) Why can you not do a direct analysis on alcohol? - correct answers because it also contains carbs, proteins, and water and these things could interfere with the analysis How do you combat this problem (in exp 1)? - correct answers -isolate the compound of interest from the rest of the compounds in the sample what is a...

V1 - correct answers volume of phase 1 (phase being extracted) V2 - correct answers volume of phase 2 (phase doing the extracting) [S]1= - correct answers Q*m/v1 [S]2= - correct answers (1-Q)*m/v2 if [H+]> Ka - correct answers D=k if [H+]< Ka - correct answers D=0 gas-gas chromatography - correct answers won't work because gases mix solid-solid chromatography - correct answers won't work because solids don't flow Velocity of solute - correct answers Vm* (1/1+K(Vs...

Increase N - correct answers 1) Increase length of column 2) Optimize flow rate (Ux) to minimize H 3) Smaller packing bead diameter, uniform packing (A-term) 4) Thinner SP layer (less C term) 5) Open Tubular Liquid Chromo (No A) (A: more sensitive & resolution, fit more plate (N) shorter analysis D: small capacity) Absorption Chromatography - correct answers SP: Solid MP: Liquid or Gas Solutes move at different rates according to the forces of attraction to the stationary phase Parti...

solvent-solvent extraction - correct answers solute is partitioning between two layers based on solubility and polarity Partition coefficient K - correct answers [S]org/[S]aq q^n=(V1/(V1+KV2)^n - correct answers q-fraction of solute left in V1 V1-volume of solvent being extracted V2-volume of solvent used to extract K-partition coefficient m-total moles of solute 1 big extraction vs many small extractions - correct answers many small extractions are better than 1 small extraction ...