Lab report / Chem
SCH4U Ms. Macklin A. Student May 28, 2020
Oxidation Inquiry Lab
Introduction
The functional group alcohols is a type of molecule in which an alkyl is bonded to a hydroxyl group (-OH). Organic chemistry, specifically alcohols are used in everyday life in terms of cosmetics, medicine and household items such as detergent. Alcohols are argued to be the most important functional group in organic chemistry due to their ability to be used and changed into different compounds (Chemistry LibreTexts, 2016) such as ketones and aldehydes (Wikipedia, 2018). The versatility of alcohols allows them to be used for industrial purposes such as a solvent or fuel (Alcohol, Carboxylic Acids and Esters, n.d.). When oxidized, primary alcohols can be changed into an aldehyde, and further into a carboxylic acid. Secondary alcohols can be oxidized into ketones, but, tertiary alcohols cannot be oxidized at all since it would require for the carbon-carbon bonds to be broken (ChemistryViews, 2017). Oxidation reactions commonly known as REDOX reactions, is a chemical reaction in which there are multiple transfers of an electron from one molecule to another. The molecule that is gaining the electron is referred to as being “reduced” as its oxidation state is negative despite the fact it is gaining an electron. The molecule losing an electron is being “oxidized,” since its oxidation state is higher. REDOX reactions crucial to biochemical reactions such as cellular respiration.
In this inquiry the oxidation of primary and secondary alcohols will be investigated to determine whether primary or secondary alcohols oxidize faster. As the carbon chain gets longer and surface area increases oxidation occurs faster due to more collisions in particles. This will be investigated by investigating alcohols with increasing carbon chains. The alcohol will be oxidized by adding a small amount of solid potassium permanganate which will then be placed in a hot water bath to accelerate the reaction. The reaction will be measured in seconds to examine which alcohol oxidizes the fastest.
Materials
Oxidizing agent: KMnO4 (potassium permanganate) Organic chemicals: 40 drops of methanol, ethanol, butan-1-ol, propan-2-ol 3 test tubes Test tube rack Bunsen burner Retort stand & ring clamp Wire mat Flint lighter Goggles
Gloves 250 mL beaker Thermometer Thermometer clamp Droppers Heat resistant pad Scoopula 200 mL of water 0.01 g scale
Procedure
1. Place goggles on face to protect eyes and put protective gloves on hands 2. Position retort stand on heat resistant pad to ensure wire mat placed on ring clamp is directly above it 3. Place bunsen burner directly under wire mat and attach it to a gas source 4. Fill 250 mL beaker with 200 mL of water and place it on the wire mat 5. Turn on the gas source connected to the bunsen burner and use flint lighter to spark a flame
6. Join thermometer clamp on the retort stand and position the thermometer within the clamp so it is not in contact with the bottom of the beaker
7. Wait until the water is at 60 degrees celsius 8. Place three test tubes in the test tube rack and use dropper to add 40 drops of methanol into each tube 9. Place watch glass on scale and zero it. Use scoopula to measure 0.5 g of potassium permanganate 10. Once the water is at 60 degrees, turn off the flame. Proceed to place a small amount of KMnO4 into each test tube
and then place them into the hot water bath. Start the stopwatch 11. Once a colour change occurs, stop the stopwatch and record observations. Record the qualitative results. 12. Repeat steps 8, 9-11 with the remaining permanganate for alcohols: ethanol, butan-1-ol and propan-2-ol.
Observations
Table 1: Amount of time it takes for the molecules in the oxidizing agent and alcohol to react and transfer an electron
Alcohol Rate of Reaction (seconds)
Trial 1 Trial 2 Trial 3 Average
Methanol 257 95 107 153
Ethanol 60 66 63 63
1-butanol 61 53 55 56.3
2-propanol 35 s 56 s 31 s 40.6
Figure 1: Average time it takes for alcohols to oxidize with potassium permanganate
Table 2: Qualitative results of the colour change in result to the oxidation of alcohols
Type of alcohol Colour change
Methanol Clear → Deep purple
Ethanol Clear → dark “muddy brown”
Butan-1-ol yellow/clear → “black” deep purple
Propan-2-ol Clear → deep purple “black”
Discussion
The purpose of this lab is to investigate the rate of reaction, specifically oxidation, in various alcohols. When an alcohol is oxidized it can be transformed into other organic molecules such as ketones and aldehydes. The oxidizing agent in this reaction will lose an electron to the alcohol which will reduce the alcohol as it is gaining the electron. As the carbon chain and surface area increases, the rate of oxidation is faster as there are more particles to react according to the collision theory. With the data collected in Table 1, this hypothesis was proven correct with 2-propanol oxidizing the fastest. Methanol took a large amount of time to oxidize with an average time of 153 seconds while 2-propanol having an average of 40.6 seconds. In Figure 1 it can be seen that the data in Table 1 formed a linear relationship representing the conclusion that as the larger the alcohol becomes, the faster it takes to oxidize.
Oxidation can be influenced by various factors and could have affected the experimental design of this inquiry. The trials were done over various days and the temperature of the environment could have changed during the trials either further inhibiting or prohibiting oxidation. In the improvement of this lab more trials would have further clarified this hypothesis and possibly have shortened the gap between methanol and ethanol in Figure 1.
Appendix
Average Formula
(Trial 1 + Trial 2 + Trial 3)/3 = average
Bibliography
Alcohol oxidation. (2018, November 22). Retrieved from https://en.wikipedia.org/wiki/Alcohol_oxidation
The Oxidation of Alcohols. (2017, May 2). Retrieved from https://www.chemistryviews.org/details/ezine/10517511/The_Oxidation_of_Alcohols.html
4. Uses of alcohol - Alcohol, carboxylic acid and esters. (n.d.). Retrieved from https://sites.google.com/site/chemistryolp/uses-of-alcohol
13.4: Reactions of Alcohols. (2019, February 23). Retrieved from https://chem.libretexts.org/Courses/Sacramento_City_College/SCC:_Chem_309_-_General,_Organic_and_Bioch emistry_(Bennett)/Chapters/13:_Functional_Group_Reactions/13.04:_Reactions_of_Alcohols