Examine the Reaction Between Benzaldehyde and Acetone or Benzaldehyde and Cyclopentanone to Form Dibenzylideneacetone or Dibenzylidenecyclopentanone

Objective: The purpose of this experiment is to examine the reaction between benzaldehyde and acetone or benzaldehyde and cyclopentanone to form dibenzylideneacetone or dibenzylidenecyclopentanone, respectively. The products will be analyzed by ultraviolet spectroscopy to determine with compound makes a better UVA sunscreen.

Procedure: For detailed procedure, please see Chemistry 235 Laboratory Manual, pages 75-78 and additional handout.1

Table 1: Reagents

Compound Molecular Weight (g/mol) Used Physical and Safety Data

3M NaOH 39.99 10.0mL= 2.2g = 0.0300 mol D=2.13 g/mL, bp 1388C. Corrosive

Benzaldehyde 106.12 1.06 g, 1.0mL = 0.0100 mol 1.0415 g/mL, bp178.1. Irritant

Cyclopentanone 84.12 8mL. 420 mg. Irritant

Ethanol 46.07 2x10mL bp 78, mp= -114. Irritant, toxic.

Chloroform 119.38 10mL mp= -63.5, bp 61.2. d= 1.483 g/mL. Harmful, irritant.

Table 2: Products

Compound Safety Amount Collected Molecular Weight (g/mol) % Yield

Dibenzylidenecyclopentanone Irritant 0.939 g 260.33 72.2%

Table 3: Ultraviolet Spectroscopy

Compound λmax Absorbance max Wavelength Range of Absorption

Dibenzylidenecyclopentanone 355.0 nm 0.825 280-410

Dibenzylideneacetone2 323.0 nm 0.375 260-375

Calculations:

%Yield:

% Yield = Actual Yield (grams)/ Theoretical Yield (grams)

Theoretical Yield = 0.005 mol (limiting reagent) * 260.33 g/mol = 1.30 g

= (0.939 g/ 1.30 g) * 100% = 72.2%

Dilution Equation for Dibenzylidenecyclopentanone:

M1V1 = M2V2

M1: 0.009g x (1mol/260.33g) = 0.000035 mol

0.000035 mol/ 0.025 L = 0.00138 mol/L

V1= x

M2 = 2x 10-5 mol/L

V2 = 0.010 L

V1= [(2x 10-5 mol/L)(0.010L)/ 0.00138 mol/L)

= 0.00014 L = 140 uL

Dilution Equation for Dibenzylideneacetone2:

M1V1 = M2V2