Comprehensive Study Notes on Organic Chemistry Laboratory Procedures and Polymer Synthesis

Purpose: To separate a mixture of compounds (Benzoic Acid, p-nitroaniline, and Naphthalene) using acid-base extraction based on solubilities and intermolecular forces.
Compounds and Properties: - Benzoic Acid ( $C_6H_5COOH$ ): MW $122.12\,g/mol$ , lit. MP $122 - 122.5\,^\circ C$ . - p-nitroaniline ( $O_2NC_6H_4NH_2$ ): MW $138.12\,g/mol$ , lit. MP $147 - 147.5\,^\circ C$ . - Naphthalene ( $C_{10}H_8$ ): MW $128.17\,g/mol$ , lit. MP $80.2\,^\circ C$ .
Experimental Results: - Benzoic Acid: $70.4\%$ recovery, MP $124.2 - 125.1\,^\circ C$ . Low recovery attributed to mechanical loss and incomplete extraction. - p-nitroaniline: $129\%$ recovery, MP $146.3 - 150.3\,^\circ C$ . High recovery and broad MP range indicate moisture or residual impurities. - Naphthalene: $90\%$ recovery, MP $83.0 - 84.1\,^\circ C$ .
Procedure Essence: Separation involves dissolving the mixture in diethyl ether, then extracting with $6\,M\,HCl$ to isolate the base (as $p\text{-nitroanilinium chloride}$ ) and $1\,M\,NaOH$ to isolate the acid (as $sodium\ benzoate$ ). The neutral naphthalene remains in the organic ether layer.

Objective: Synthesize n-butyl bromide from 1-butanol via a nucleophilic substitution ( $S_N2$ ) reaction.
Reaction Reagents: $Sodium\ bromide\ (NaBr)$ , $water\ (H_2O)$ , and $concentrated\ H_2SO_4$ . $HBr$ is generated in situ.
Mechanism: Protonation of the hydroxyl group converts it into a good leaving group ( $H_2O$ ), followed by bromide ion attack.
Theoretical Yield: $14.19\,g$ .
Actual Results: Actual mass $2.27\,g$ , percent yield $15.7\%$ , experimental BP $101.9\,^\circ C$ (lit. $101.3\,^\circ C$ ).
Purification: Consists of reflux for $60\,minutes$ , followed by extraction with $9\,M\,H_2SO_4$ , $H_2O$ , and $saturated\ NaHCO_3$ . Final drying uses anhydrous $CaCl_2$ .

Objective: Synthesis of cyclohexene through the acid-catalyzed dehydration of cyclohexanol.
Mechanism: $E1$ elimination involving a secondary carbocation intermediate.
Yield Calculations: Theoretical yield $16.43\,g$ (starting from $20.09\,g$ cyclohexanol). Experimental yield $11.27\,g$ ( $68.7\%$ recovery).
Physical Properties: Experimental BP range $81.0 - 85.4\,^\circ C$ (lit. $83.0\,^\circ C$ ).
Qualitative Tests: - Bromine Water: Decolorized from red/orange to clear, confirming the presence of a double bond. - $KMnO_4$ : Purple solution formed a brown precipitate ( $MnO_2$ ), positive for alkene.
Spectroscopy: IR confirmed $sp^2\ C-H$ stretch above $3000\,cm^{-1}$ and absence of $O-H$ stretch. $^1H\text{ NMR}$ showed vinylic protons at $\delta\ 5.7\,ppm$ .

Purpose: Synthesize benzopinacolone from benzopinacol via a one-step carbocation rearrangement.
Reagents: $Glacial\ acetic\ acid$ , $iodine\ (I_2)$ , and $benzopinacol$ .
Mechanism: Protonation of an alcohol leads to water loss, followed by a benzene ring shift to form a resonance-stabilized ketone.
Experimental Data: Theoretical yield $5.23\,g$ . Actual pure yield $5.135\,g$ ( $98.18\%$ ).
Melting Point: Experimental $183.7 - 185.9\,^\circ C$ (lit. $182.0 - 184.0\,^\circ C$ ).

Classification: - Addition Polymers: Monomers add without loss of atoms (e.g., polystyrene, polyethylene, PVC). - Condensation Polymers: Formed with the elimination of small molecules like $H_2O$ (e.g., nylon, polyesters). - Thermal: Thermoplastics (recyclable, flexible) vs. Thermoset plastics (cross-linked, rigid).
Synthesis Projects: - Linear Polyester: From phthalic anhydride and ethylene glycol. - Cross-linked Polyester (Glyptal): From phthalic anhydride and glycerol. - Nylon 6-6: From hexamethylenediamine and adipoyl chloride at the liquid-liquid interface. - Polystyrene: Free-radical polymerization of styrene monomer using benzoyl peroxide initiator.
Notes on Texture: Polyesters are gummy/sticky; Nylon is thin, stretchy, and delicate.

Immiscible Definitions: Liquids that do not mix to form a uniform solution, such as wax and water in a lava lamp.
Extraction Efficiency: Mathematical proof shown that three smaller extractions (e.g., $3 \times 25\,mL$ ) recover significantly more mass (e.g., $10.72\,g$ vs. $10.1\,g$ ) than one large extraction ( $1 \times 50\,mL$ ) when $K = 4.2$ .
Purification Steps in Substituted Alkanes: - $9\,M\,H_2SO_4$ : Protonates impurities to increase aqueous solubility. - $NaHCO_3$ : Neutralizes acidic components. - $Anhydrous\ CaCl_2$ : Removes trace residual water.
NMR and Spectroscopy: - Nitrogen rule: Used to discern the presence of nitrogen based on molecular ion mass. - Integration: Proportional to the number of hydrogens at a specific chemical shift ( $\delta$ ). - Splitting: Determined by the $N+1$ rule, providing information on adjacent protons.
** Dialogue/Interaction regarding Synthesis of 1-Bromobutane**: - *Question*: What is the purpose of cooling in an ice bath before adding $H_2SO_4$ ? - *Response*: Adding concentrated $H_2SO_4$ is highly exothermic; the ice bath prevents overheating, reduces risk of side reactions, and improves safety.
Dialogue/Interaction regarding Cyclohexene: - Question: How do you check which layer is the aqueous layer during extraction? - Response: Add a drop of water. If it mixes, it is the aqueous layer; if it forms a droplet, it is the organic layer.