Chemical Synthesis and Lab Safety Study Notes

Lab Safety & Procedures

• Gloves Removal in Lab
    - Must remove gloves before leaving the laboratory as per SOP for Wearing Gloves.
    - Never wear gloves in hallways, elevators, or when touching door handles.
    - This policy is in place to prevent the spread of chemical contaminants to public areas.

Triethylene Glycol in Luminol Synthesis

• Purpose of Triethylene Glycol
    - Used as a high-boiling point solvent with a boiling point of 285°C.
    - Facilitates the reaction mixture of 3-nitrophthalic acid and hydrazine to reach high temperatures necessary for the double amination step while keeping reagents in solution.

Chemical Synthesis Questions

• High Heat Requirement for 3-Nitrophthalhydrazide Formation
    - High heat is essential to overcome activation energy.
    - The formation of the cyclic diamide requires sufficient energy to facilitate the nucleophilic attack and subsequent dehydration.

Intersystem Crossing in Electron States

• Movement of Electrons from Singlet to Triplet State
    - Electrons transition from the singlet state to the triplet state in a process known as intersystem crossing.
    - The triplet state is lower in energy (more stable) than the singlet state.

Intermediate Compounds in Luminol Synthesis

• Components of the 7th Intermediate
    - 1) Luminol dianion
    - 2) Luminol radical anion
    - 3) Superoxide adduct (hydroperoxide)
    - 4) Cyclic peroxide (endoperoxide)
    - 5) Excited state 3-aminophthalate dianion
    - 6) Light emission step
    - 7) 3-aminophthalate dianion (Ground State)

Emergency Response for Electrocution

• SOP for Electrocution Response
    - Do NOT touch the person being electrocuted; this places you at risk of electrocution as well.
    - Turn off the power source immediately:
      - Options include unplugging the equipment or using the circuit breaker (emergency power shut-off).
    - Call for help:
      - Once power is shut off, call 911 or alert the teaching assistant/instructor for immediate medical assistance.

Percent Yield Calculation for Luminol Synthesis

• Luminol Reaction Equation
    - $3 ext{-}nitrophthalic ext{ acid} + ext{hydrazine} <br>ightarrow ext{luminol} + ext{byproducts}$
    - Determine limiting reagent:
       - If n_{A} < n_{ ext{μ}}, then 3-nitrophthalic acid is limiting.      - If n_{A} > n_{ ext{μ}}, then hydrazine is limiting.
       - Let $n_{lim} = ext{min}(n_{A}, n_{ ext{μ}})$.

• Convert Given Masses to Moles
    - Use molar masses (approximate):
      - Molar mass of 3-nitrophthalic acid: $M = 211.13 ext{ g/mol}$
      - Molar mass of hydrazine: $M ext{ (N}_2 ext{H}_4 ext{)} ext{ }{ ext{approx. }} 32.05 ext{ g/mol}$
      - Molar mass of luminol: $M ext{ (C}_8 ext{H}_7 ext{N}_3 ext{O}_2 ext{)} ext{ }{ ext{approx. }} 177.16 ext{ g/mol}$
  

• Calculating Moles
    - $n_A = rac{m_A}{211.13}$
    - $n_{ ext{μ}} = rac{m_{ ext{μ}}}{32.05}$

• Calculate Theoretical Yield of Luminol
    - The stoichiometric ratio to luminol is 1:1:
      - Therefore, $n_{ ext{luminol, theo}} = n_{lim}$.
  

• Calculate Percent Yield
    - Theoretical mass of luminol:
      - $m_{ ext{theo}} = n_{ ext{luminol, theo}} imes 177.16$
    - Percent yield calculation:
      - Given actual mass of luminol, $m_{ ext{prod}}$:
      - ext{Percent Yield} = rac{m_{ ext{prod}}}{m_{ ext{theo}}} imes 100 ext{%}

Triplet vs. Singlet States

• Triplet vs. Singlet Energy Levels
    - The triplet state ($T_1$) is lower in energy than the singlet state ($S_1).
    - Reason: As per Hund’s Rule, electrons in a triplet state have parallel spins and occupy different spatial orbitals, reducing electron-electron repulsion compared to paired spins in a singlet state.

Phosphorescence

• Color Emission in Phosphorescence
    - The emitted color related to phosphorescence is Green.
    - This occurs from the lower-energy triplet state ($T_1 <br>ightarrow S_0$).
    - Lower energy corresponds to a longer wavelength, which shifts emission from standard blue fluorescence (~465 nm) towards green.
  

Color Changes of Azo Violet

• Under acidic conditions: Color changes to orange.

• Under basic conditions: Color changes to purple.

Effects of Functional Groups on Reactivity

• Influence of Functional Groups
    - Electron withdrawing groups:
      - Decrease electron density of the ring.
      - Result in lower nucleophilicity and slower reaction rates compared to benzene.
    - Electron donating groups:
      - Increase electron density of the ring.
      - Result in higher nucleophilicity and faster reaction rates compared to benzene.

• Ortho/Para Directing Nature
    - Functional groups affect rate and ring activation, showing ortho and para directing behavior for substituted benzene reactants.