SN1 and SN2 Reactions using Alkyl Halides (2018 05 31 03 01 51 UTC) PDF

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Name: Course: Organic Chemistry Laboratory and Recitation II Instructor: Date: PART I-SUPPLEMENT FOR NUCLEOPHILIC SUBSTITUTION REACTIONS USING ALKYL HALIDES: SN1 AND SN2 REACTIONS

SN2 Reaction  

Nucleophile: NaI or I¯ Solvent: Acetone R⸻X + NaI (/acetone) → R⸻I + NaX↓ SN1 Reaction

 

Nucleophile: AgNO3 or NO3¯ Solvent: Ethanol R⸻X → R ⁺ + X ⁻+ AgNO3 → NO3⁻ + AgX↓

PART II-SYNTHESIS OF TRITYL METHYL ETHER

The goal of these experiments is to determine the development of eight alkyl halides such as: 1-chlorobutane (1), 1-bromobutane (2), 2-chlorobutane (3), 2-chloro-2-methylpropane (4), bromobenzene (5), 2-bromobutane (6), 2-bromo-2-methylpropane (7), & 1-chloro-2methylpropane (8) throughout nucleophilic substitutions SN1 and SN2 reactions while observing the conditions and substrate structures. All alkyl halides substrates will be tested in different test tubes at room and elevated temperatures into a solution of NaI in acetone (18%) in order to determine the SN2 reaction. On the other hand, another set of eight tubes will be tested at room and elevated temperature and in a solution of AgNO3 silver nitrate in ethanol to determine the SN1 reaction. The formation of a precipitate, by initial reaction or by heating, will indicated the accuracy of the reactions. The Second of the experiment will be executed thru Synthesis of Trityl Methyl Ether where its end results will occur by purification through crystallization and the melting point will be obtained accordingly.

Procedure: PART I-SUPPLEMENT FOR NUCLEOPHILIC SUBSTITUTION REACTIONS USING ALKYL HALIDES: SN1 AND SN2 REACTIONS

The procedure will be executed by one party while working under hood and wearing gloves for this part of the experiment. 1) 0.1 ml of alkyl halides substrates was put in eight clean 10X75mm test tubes which were labeled according: 1-chlorobutane (1), 1-bromobutane (2), 2-chlorobutane (3), 2-chloro-2-methylpropane (4), bromobenzene (5), 2-bromobutane (6), 2-bromo-2-methylpropane (7), & 1-chloro-2methylpropane (8). 2) Meanwhile, 1 ml of NaI sodium iodide in acetone (18%) was poured on the side for the SN2 reaction purpose. 3) After all, eight tubes were filled by their respective amount. Using a Pasteur pipette, five drops equivalent to 0.25 ml of NaI sodium iodide in acetone (18%) was dropped in each tube while closely observing the reaction transformation at room and elevated 50°C water bath temperatures during a strict timeframe of 5 minutes for each sample. 4) In fact, many different compounds states, precipitates and color were observed which was discussed in detail in the SN2 reaction Chart in this report. 5) SN1 Reaction occurred by refilling eight clean tubes with the same Alkyl halides substrates. They were labelled according within the same order. 6) Then, the tubes were filled by their respective amount. Using a Pasteur pipette, five drops equivalent to 0.25 ml of AgNO3 silver nitrate in ethanol was dropped in each tube while closely observing the reaction transformation at room and elevated 50°C water bath temperatures during a strict timeframe of 5 minutes for each sample.

7) As previously seen from the other reaction, many different compounds states, precipitates and color were observed which was discussed in detail in the SN1 reaction Chart in this report. 8) The last phase was obtaining 0.1ml of 2-bromobutane and 2-chlorobutane in two test tubes and 10 drops equivalent to 0.5 ml of AgNO3 silver nitrate in ethanol were added into each tube. Thus, precipitates and color were observed which was discussed in detail in the SN1 Reaction of 2chlorobutane and 2-bromobutane in a AgNO3 Silver Nitrate in ethanol Chart in this report.

SN2 Reaction: Observation with naked eye. 0.1 ml Alkyl Halides

Compounds state at room

Compounds state when

Substrates in test tubes.

temperature when mixed

tubes placed in the heated

with 5 drops≈ 0.25 ml of

50°C water bath for 5

1-chlorobutane (1) 1-bromobutane (2)

NaI in acetone (18%). Clear Light precipitate seen Yellow solution without

minutes. Cloudy precipitate seen Yellow and precipitate seen

2-chlorobutane (3) 2-chloro-2-methylpropane (4)

precipitate Cloudy with Mild Precipitate Clear with no reaction

Cloudy with more precipitate Precipitate layer and liquid

bromobenzene (5)

Cloudy with heavy

evaporated. Heavy precipitate remained

2-bromobutane (6)

precipitate Lightly cloudy with mild

Lightly cloudy with

precipitate 2-bromo-2-methylpropane (7) Yellow with no precipitation

precipitate seen Yellow with precipitation

1-chloro-2-methylpropane (8)

seen No reaction same state

Lightly yellow with cloudy precipitate

SN1 Reaction: Observation with naked eye

0.1 ml Alkyl Halides

Compounds state at room

Compounds state when

Substrates in test tubes.

temperature when mixed

tubes placed in the heated

with 5 drops ≈ 0.25 ml of

50°C water bath for 5

1-chlorobutane (1)

AgNO3 in ethanol. Slightly Cloudy with

minutes. No reaction same state

1-bromobutane (2)

precipitate seen Heavy Cloudy precipitate

No reaction same state

2-chlorobutane (3)

scattered Light cloudy with

Clear on top layer and heavy

precipitation seen

layer of precipitation displayed at the bottom of

2-chloro-2-methylpropane (4) bromobenzene (5) 2-bromobutane (6)

Clear with precipitate seen

tube Precipitate layer and liquid

Cloudy with no precipitation Yellowish with precipitate

evaporated No reaction same state Yellow with heavy precipitate

displayed at the bottom 2-bromo-2-methylpropane (7) Yellow with light

1-chloro-2-methylpropane (8)

displayed at the bottom Dark yellow with small

precipitation seen

amount of solution and

Cloudy with no Precipitation

precipitate displayed Slightly cloudier with light precipitate.

SN1 Reaction of 2-chlorobutane and 2-bromobutane in a AgNO3 Silver Nitrate in ethanol. 0.1 ml Alkyl Halides

Compounds state at room

Compounds state when

Substrates in test tubes

temperature when mixed

tubes placed in the heated

with 10 drops ≈ 0.5 ml of

50°C water bath for 5

2-chlorobutane

AgNO3 in ethanol Cloudy with no precipitation

minutes Cloudy heavy precipitate

2-bromobutane

Slightly yellowish and

centered at the bottom Yellow and Cloudy and

Cloudy no precipitation

Yellow precipitate centered at

formed

the bottom layer.

PART II-SYNTHESIS OF TRITYL METHYL ETHER The procedure will be executed by one party while working under hood and wearing gloves especially for the corrosive Sulfuric Acid used during the experiment.

1) 100mg of Triphenylmethanol was properly weight in the laboratory scale which was already grinded to fine powder and placed into a tube. Then, 1 ml of Sulfuric acid which was collected under the hood fume because it was very corrosive and double gloves was worn for precautionary measure. As the Sulfuric acid was added into the tube, with the fine powder of TPM, the new solution turned yellow.

2) Using a stir stick the triphenylmethanol was stirred until the compound changed from yellow to Black which was a great indication that the TPM had completely dissolved.

3) Then, 2ml of ice cold methanol was added into tube and the tube was place in ice for an additional 10 minutes. After it was removed from the ice, the tube was very warm. The reason was unknown.

4) Then, the product was put into vacuum filtration, but no crystallization occurred. Therefore, the situation was brought up to the instructor attention which advised to scrape the brown and gray solid residual crystal like thin layer in the filter by obtaining the weight which was 0.024mg. Then, melting point obtained was 110120°C.

Conclusion: The goal of these experiments was to determine the development of eight alkyl halides such as: 1-chlorobutane (1), 1-bromobutane (2), 2-chlorobutane (3), 2-chloro-2-methylpropane (4), bromobenzene (5), 2-bromobutane (6), 2-bromo-2-methylpropane (7), & 1-chloro-2methylpropane (8) throughout nucleophilic substitutions SN1 and SN2 reactions while observing the conditions and substrate structures. All alkyl halides substrates were tested in different test tubes at room and elevated temperatures into a solution of NaI in acetone (18%) in order to determine the SN2 reaction. On the other hand, another set of eight tubes were tested at room and elevated temperature and in a solution of AgNO3 silver nitrate in ethanol to determine the SN1 reaction. The Second of the experiment will be executed thru Synthesis of Trityl Methyl Ether where its end results will occur by purification of the compounds through crystallization and the melting point which was obtained. The first part was a considered a success because formation of precipitates and the color changes from the tubes thru the SN1 and SN2 reactions indicated the accuracy of the experiment. On the Other Hand, the second part “synthesis of trityl methyl ether” wasn’t perfectly done or pure because the crystallization wasn’t formed which affected the weight of the product and its melting point. Consequently, errors in the experiment may have been a result of mistakenly adding to many solutions into the tube which could alter the identification of the compounds or eventually human error.

Reference: Williamson, K., & Masters, K. (2011). Macroscale and Microscale Organic Experiments. Belmont: Cengage Learning pg 318-325 and pg 444-446 ....