Organic Chemistry Lab Final study Guide
Organic Chemistry Lab Final study Guide CHEM 312
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This 5 page Study Guide was uploaded by Cassian Bellino on Friday March 4, 2016. The Study Guide belongs to CHEM 312 at California Polytechnic State University San Luis Obispo taught by Kevin Kingsbury in Winter 2016. Since its upload, it has received 116 views. For similar materials see Survey of Organic Chemistry in Chemistry at California Polytechnic State University San Luis Obispo.
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Date Created: 03/04/16
Key concepts to remember from each lab 1. Lab One Structure and Isomerism A molecular formula gives the actual number of atoms of each element in a compound Structural formula shows only how the atoms are connected Condensed formula is an abbreviated way to show structure (every end point or vertex is a carbon with hydrogens assumed to be connected to it, whereas every other atoms is written on and attached hydrogens are written) Structural Isomers are two molecules with the same formula but different arrangement/connections Geometric Isomers are two molecules with the same formula and same arrangement/shape but differing 3D shapes (same connections of carbon chain but with a differing placements of double bonds to restrict imitation) Stereoisomers are the head group for geometric isomers representing compounds of differing 3D spatial arrangement 2. Lab Two TLC, Functional Groups, Solubility TLC The Thin Layer Chromatography is a white POLAR plate made of oxygen and silicon. POLAR compounds react with plate and do not move very far NONPOLAR compounds do not react with plate and move far POLAR solvent will move dots farther up plate (EtOAc or MeOH) NONPOLAR solvents stay close (Heptane) Nonpolar compounds (move far)? -> use a nonpolar solvent to separate them Nonpolar solvent- move far/ polar compound- don’t move far Each spot represents one component in the mixture; # of spots = # of components in mixture Advantages of TLC- fast, cheap, simple, works for solids & liquids, don’t have to use volatile samples, Disadvantages of using TLC- TLC cannot tell the amount of a present compound Functional Groups Use TLC to determine if functional groups are present Spray Ninhydrin on TLC plate + heat to detect amine (NH2) groups Shows up bright yellow under UV light (if amine is present) Solubility Soluble in water= miscible Insoluble in water= immiscible Compounds containing oxygen (polar) were soluble in water Hydrocarbons are insoluble More O:C ratio makes hydrocarbon more polar/soluble in water 3. Lab Three Column Chromatography Think of Column Chromatography as an upside down TLC plate and instead of dots travelling up via solvent, it is now larger quantities of a mix of liquid compounds travelling down via gravity and separating via solvent Use a solvent of optimal polarity (diluted, then decreasing in dilution), and collect separated mixture in test tubes to test on a TLC plate Advantages of CC- any type of compound can be isolated from a column Disadvantages- time consuming, expensive Least POLAR compounds will run through polar solvent and exit column first Most POLAR compounds will react with polar solvent and remain in column the longest Silica Gel must be handled under fume hood due to risk of lung irritation Water was not used as a solvent because it dissolves silica gel Order of materials from bottom of column (spout) to top: Cotton, sand, silica gel, compound mixture, solvent (on top) Used least polar solvent -> most polar solvent to slowly react/separate the least polar compounds to more polar compounds Skipping the diluted solvents and using just the strongest solvent (all acetone) would make all the compounds run/mix together When testing on TLC plate it is necessary to apply/ larger quantities on plate since compounds are very dilute 4. Lab Four Steam Distillation Steam distillation is used to separate a naturally occurring oil from its corresponding spice Advantages of steam distillation- easy to remove water insoluble compounds from non-volatile compounds in reaction mix Steam Dist- BP is below lowest BP of two compounds used (with H O2 BP < 100 C) Simple Dist- BP is between BP’s of both compounds; starts at lower BP and ends up below higher BP Fractional Dist- Temp starts at lower BP [of both compounds] and shoots straight up to higher BP then remains there. (backwards Z) Solubility Demo in lab Solubility increases in water as temperature increases due to the added energy needed to break bonds between IMFs and help those broken molecules be attracted to/react with other molecules Reactant bonding vs Product bonding differs in the way that added/lost energy will occur and will change the geometric shape of the molecule, resulting in lone pairs and/or charges 5. Lab Five Extraction and Crystallization Extraction works on the principle of different solubility; compound has different solubility in different solvents Materials with no attraction WILL NOT dissolve in one another Use Salicydic acid, dissolved it in a (NaOH) base to make it into an IONIC solution (water soluble) Water soluble/ charged salicydic acid + acid = voluminous white precipitate Chemicals can be extracted if one of the compounds has a “handle” differentiating it from the other compounds (acid/base chemistry) We dissolved unknown mixture with ethyl acetate to dissolve all the compounds, then added an acid to isolate the base (amine), it will neutralize and remain i2 H O portion of the separated liquid which can be pipetted out of separated solution. Add base to extract acid into 2 O layer/pipet out. Extraction, TLC, Column Chromatography all work to isolate /identify one unknown/known compound in a mixture % Recovery= (solubility of compound @ BP- solubility of compound @ 0)/solubility @ BP x 100 High %= high recovery of extracted compound Crystallization COMPOUNDS ARE MORE SOLUBLE IN A HOT SOLVENT THAN A COLD SOLVENT Solvent must be soluble in hot water and relatively soluble in cold water Impurities must be insoluble in hot water or soluble in cold water Solvent cannot react with product Solid is dissolved in hot/boiling solvent, impurities are removed by rapid/hot/gravitational filtration Filtered solution is cooled slowly (so no impurities are trapped in crystal) Rinse dirty solvent containing dissolved impurities off crystals with cold solvent The most efficient way to isolate a solid from a liquid is by vacuum; much more forceful and only leaves solid behind 6. Lab Eight Polymers Two types of polymer synthesis: 1) step-growth 2) chain growth “assembling a pearl necklace” Nylon is made through interfacial polymerization Crosslinking gives more rigidity and movement to polymers Nylon is made by the polymerization of a Halide and NH 2mine Materials to make nylon are corrosive and cause inhalation hazards (hexamethylenediamine and adipoyl chloride solution into cycloheaxane) The reaction/polymerization for nylon takes place at the interface between layers NaOH neutralizes the HCl Slime/Silly Putty Slime= Hydrolysis of polyvinyl acetate and polyvinyl alcohol with borax acting as the cross linker Silly Putty= Elmer’s Glue + borax Polymers Demo Polyacrylic acid (PAA) is a super absorbent polymer Carboxylic functional group H-bonds with multiple water molecules and can absorb up to 800 times its volume, providing a physical form from the PAA Temperature will remain constant during a phase change Material coated in PAA and lit on fire, only the PAA will catch fire water will absorb the heat Carboxylic acid on PAA can also deprotonate into an ion state and use a metal to crosslink to purify water 7. Lab Eight Synthesis and Color The color of material is related to the difference in energy between the ground state and the excited state of the molecules in the material Photons with equal energies to those energies of a certain material will be absorbed Photons not absorbed are transmitted/reflected by the material, defining the color of the material Double bonds conjugated by single bonds are just a series of atoms with adjacent overlapping P orbitals Salicylaldehyde and 2-aminophenol react (with ethanol as a solvent) and bind creating conjugated bonds and creating a highly colored solid This reaction of creating an amine and can be shifted using Le Chatlier’s Principle Le Chatlier’s Principle: if a stress is places on a system, the system responds to relieve the stress. Add stress to one side of reaction -> reaction shifts in accordance to relieve stress and maintain equilibrium Florescence: a photon moves an electron to an excited state, which is unstable, and begins to return to a less excited state—first shortly with a short high energy emission of energy, then followed by a slower, less energized drop emitting long wavelengths 8. Lab Nine Soap and Biodiesel Biodiesel Esters are known for causing the smell and flavor in many fruits Esterification: carboxylic acid + alcohol (using a catalyst) and heat to improve the rate of attaining equilibrium Transesterification: replacing one ester group with another Saponification: cleavage of an ester bond into a carboxylic acid salt and alcohol with a base Catalytic base is added to reaction mixture to deprotonate the alcohol and increase nucleophilic behavior (has more electrons/wants positive charge) This deprotonation is conducted three times to displace the triglyceride into glycerol Soap Fats and vegetables are triesters if glycerol which contain fatty acids with 12-18 carbon chains Fats are saturated (All the spots for hydrogen are filled), solid at room temp Oils are unsaturated with double bonds between carbons, liquid at room temp Saponification is the ester separated into the alcohol, glycerol, and sodium salt of the acid Sodium salt of the acid= soap Detergent of soap relies on hydrophilic end and lipophilic end required to disperse oily dirt, keeping it suspended so it can be washed away Short chains = suds (not necessarily helpful for cleaning) Long chains = wash better Calculating moles of present compound: Given mass (g) x (1 mol/molecular mass of one compound) Theoretical Yield: Given x molecular weight x stoichiometry/mol to mol ratio of one compound to another x molecular weight of wanted compound Percent Yield: (Actual yield / theoretical yield) x 100
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