Lab Safety Guidelines and Techniques

Lab Safety Guidelines

• Chemical Splash: Flush affected area with eyewash station for at least 15 minutes.
• Corrosive Chemicals: Immediately flush contaminated area with copious amounts of water. Corrosive chemicals cause visible destruction or permanent changes in human skin tissue.
• Flammable Liquids: Remove and turn off all sources of ignition in case of spill. Use spill pads to clean up, then place used absorbent materials in sealed, labeled, heavy-duty poly-bags for disposal.
• Disposing of Excess Acids/Bases: Neutralize excess with appropriate reagents (like sodium bicarbonate), check pH with paper, and then pour down sink (unless organic solvent is present).
• Inorganic Solid Waste: Dispose of dry inorganic solid waste (like CaCl2) in biohazard waste boxes.

Lab A/B: Reactions and Techniques

• Equivalent: A ratio of reactants used in a chemical reaction. For example, acetic anhydride and salicylic acid react in a 1:1 ratio.
• Hydrolysis: A reaction involving the breaking of a chemical bond by the addition of water.
• Base-Promoted Hydrolysis: The base (OH-) acts as a nucleophile, participating in the reaction and forming part of the product but not being regenerated later.
• Triacylglycerol Hydrolysis: The cleavage of three ester bonds in a triacylglycerol molecule produces glycerol and three long-chain fatty acids.
• Stoichiometry Concepts:
  • Theoretical Yield: The maximum amount of product achievable assuming 100% conversion of the limiting reactant.
  • Limiting Reactant: The reactant present in the smallest amount, determining the maximum amount of product possible.
  • Percent Yield: The ratio of actual yield to theoretical yield.
  • Multistep Synthesis: The overall percent yield is calculated by multiplying the yield of each step expressed as a decimal.
• Recrystallization: A purification technique for solid organic compounds using a solvent that dissolves the compound when hot but not when cold.
• Vacuum Filtration: A technique for quickly and efficiently separating a solid from a liquid mixture.
• Chromatographic Techniques:
  • Thin Layer Chromatography (TLC): Separates compounds based on their affinity to a stationary phase (Silica gel or Alumina) and a mobile phase (a liquid).
  • Liquid Chromatography (LC): Similar to TLC but uses a column packed with stationary phase and a liquid mobile phase.
  • High Performance Liquid Chromatography (HPLC): Uses high pressure to force the mobile phase through a small-diameter column, increasing separation efficiency.
  • Gas Chromatography (GC): Separates volatile compounds based on their vapor pressure and interactions with a non-volatile stationary phase using a gas mobile phase.
• Silica Gel: A common, inexpensive stationary phase in chromatography. Its high polarity results from silanol (Si-OH) groups on its surface. More polar molecules interact more strongly with silica gel, leading to slower movement on the TLC plate.
• Rf Value: Ratio of distance traveled by a solute to the distance traveled by the solvent in TLC. Rf values are indicative of compound polarity.

Lab E: Diels-Alder Reaction

• Cycloaddition Reaction: A 1,4-addition of a conjugated diene and an alkene to form a new six-membered ring.
• Diels-Alder Reaction Characteristics:
  • Thermal cycloaddition reaction, meaning it requires heat.
  • Concerted reaction, where bond formation occurs simultaneously.
  • Formation of two new sigma bonds and one new pi bond.
  • Formation of a new six-membered ring.
• Diene Reactivity: Dienes must be in the s-cis conformation for reactivity.
• Dienophile Reactivity: Electron-withdrawing groups make dienophiles more electrophilic and reactive.
• Butadiene Sulfone: Used as a convenient source of 1,3-butadiene, which is a gas at room temperature.
• Xylene: A solvent used in the Diels-Alder reaction to provide heat.
• Refluxing: Heating a reaction mixture at its boiling point to maintain a constant temperature and prevent loss of material from the reaction flask.
• 3-Sulfolene: A non-hygroscopic solid used as a source of 1,3-butadiene. Its use prevents flammability hazards, as butadiene and SO2 are gases at room temperature.

Lab F: Fischer Esterification Reaction

• Refluxing: Heating a reaction mixture at its boiling point to maintain a constant temperature and prevent loss of material from the reaction flask.
• Purification Techniques: Methods used to separate and purify products.
  • Recrystallization: For purifying solid compounds.
  • Thin Layer Chromatography (TLC): For monitoring reaction progress and assessing purity.
  • Extraction: Used to separate compounds based on their solubility in different solvents.
  • Distillation: For purifying liquid compounds.
    • Simple Distillation: Separates liquids with boiling points differing by at least 100 degrees Celsius.
    • Vacuum Distillation: Distilling compounds with high boiling points or those that decompose near their boiling point.
    • Fractional Distillation: Separates liquids with boiling points close together, using a fractionating column to increase the number of vaporization-condensation cycles.
• Boiling Point Factors:
  • Molecular Weight: Larger molecules have higher boiling points.
  • Intermolecular Interactions: Stronger intermolecular interactions (like hydrogen bonding) lead to higher boiling points.
• Waste Disposal:
  • Red Sharps: Glass waste.
  • Biohazard: Gloves and paper towels.
  • Silica Gel: Powder waste (inhalation hazard).
  • Acetone: Non-halogenated waste unless used to clean DCM.

IR Spectroscopy

• Purpose: Used to identify functional groups present in a molecule.
• IR Absorptions: Occur due to stretching or bending of covalent bonds in molecules.
• Transmittance: The amount of light passing through the sample.
  • 100% transmittance: All light passes through.
  • 0% transmittance: All light is absorbed.
• Diagnostic Region: Used to identify functional groups.
• Fingerprint Region: Unique to each molecule, used to identify the compound through spectral comparison.
• Wavenumber: Proportional to frequency and inversely proportional to wavelength, related to a specific covalent bond vibration.

NMR Spectroscopy

• Purpose: Provides information about the structure of a molecule.
• Nuclei: Possess charge and can spin, generating a magnetic dipole.
• Nuclear Magnetic Spin Quantum Number (I): Determines the magnetic properties of a nucleus.
  • I=0: No nuclear spin (e.g., 12C)
  • I=1/2: Spin 1/2 (e.g., 1H, 13C)
  • I=1: Spin 1 (e.g., 14N)
• NMR Signal: A resonance signal that is unique to each type of proton or carbon in a molecule.
• Chemical Shift: The position of a signal in a NMR spectrum, measured relative to a standard reference compound.

This quiz covers essential lab safety guidelines including procedures for dealing with chemical spills, disposal of hazardous materials, and the handling of corrosive substances. Additionally, it addresses key concepts related to chemical reactions and equivalent ratios, ensuring a comprehensive understanding of lab practices.