User:Elizabeth Ghias/Notebook/Experimental Chemistry/2013/02/01

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<u>Isopropanol Solution Preparation<u>
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<u>Isopropanol Solution Preparation</u>
Next, we tested the concentrations of isopropanol that can bind to the OH groups in 0.5 g PVOH.  We decided to start with 10% OH groups bound to isopropanol and decrease the concentration from there.   
Next, we tested the concentrations of isopropanol that can bind to the OH groups in 0.5 g PVOH.  We decided to start with 10% OH groups bound to isopropanol and decrease the concentration from there.   

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Experimental Chemistry Main project page
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Objective

To calculate the number of OH groups in polyvinyl alcohol (MW = 146000 - 186000) and to prepare PVOH films

Description

OH Group Calculations

  • Because we will be using PVOH MW = 146,000 to 186,000, we will calculate the minimum, maximum, and average number of OH groups in a molecule of PVOH.

PVOH repeating unit structure = CH2-CH-OH → MW = 12·2+4+16 = 44

MW min: 146,000/44 = 3318.13 PVOH units per molecule → 3318.13 OH groups per molecule

MW max: 186,000/44 = 4227.27 units per molecule → 4227.27 OH groups per molecule

MW avg: 166,000/44 = 3772.73 units per molecule → 3772.73 OH groups per molecule

  • Used 3772.73 OH groups per molecule to find the number of OH groups in 0.5 grams of PVOH

0.5g PVOH / 166,000 g/mol = 3.012E-6 moles PVOH

3.012E-6 moles PVOH × 3773.73 OH groups per molecule = 0.0114 OH groups in 0.5 g PVOH

0.0114 OH groups in 0.5 g PVOH · 6.022 x 1023 molecules/mol = 6.86508 x 1021 OH groups in 0.5 g PVOH


Isopropanol Solution Preparation

Next, we tested the concentrations of isopropanol that can bind to the OH groups in 0.5 g PVOH. We decided to start with 10% OH groups bound to isopropanol and decrease the concentration from there.

[6.86508 x 1021 OH groups x 1 molecule isopropanol/1 molecule OH] / 6.022 x 1023 molecules/mol = 0.00114 moles isopropanol

0.00114 moles isopropanol x 60.1 g/mol = 0.068514 g isopropanol

0.068514 g isopropanol / 0.786 g/mL = 0.0872 mL isopropanol

Isopropanol solutions were then prepared by taking 10 mL of isopropanol (see notes) and putting it in a tube. Serial dilutions with water were then carried out to create 10%, 1% and 0.1% solutions. To create these solutions, 1 mL of solution was added to 9 mL of water. 0.872 mL of each solution was added to its respective film.


Films Prepared

All films were heated on a hot plate until the PVOH dissolved in the water. For films 5,6, and 7, additional water was added to the gel to assist in the dissolution. Once dissolved, the film was removed from heat and any additional reagents were added while the gel was stirred. When isopropyl and glutaraldehyde were added, the isopropyl would be added first and then would stir for roughly 2 to 3 minutes. Glutaraldehyde was added last. Once prepared, the films were poured into a large plastic dish and were allowed to evaporate over the weekend.

  1. 0.5043 g PVOH + 6 mL water (this was the only small film prepared)
  2. 0.5027 g PVOH + 6 mL water + 1 mL glutaraldehyde
  3. 0.5029 g PVOH + 6 mL water + 87 μL isopropyl stock solution + 1 mL glutaraldehyde
  4. 0.5029 g PVOH + 6 mL water + 87 μL 10% isopropyl solution (see notes) + 1 mL glutaraldehyde
  5. 0.5060 g PVOH + 6 mL water + 87 μL 1% isopropyl solution + 1 mL glutaraldehyde
  6. 0.5034 g PVOH + 6 mL water + 87 μL 0.1% isopropyl solution + 1 mL glutaraldehyde
  7. 0.5050 g PVOH + 6 mL water


Data

  • No data was collected today

Notes

  • 87.2 μL isopropanol solution corresponds to the amount of isopropanol needed to bind 10% of the OH groups in PVOH. In the serial dilutions, because the concentration has been reduced by a factor of 10%, the same volume (87.2 μL) of the diluted solutions could be added to films



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