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Organic lab. Comparison of alkanes and alkenes

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Introduction

Vita Salvioni Guttmann Chemistry III HL 22-10-2012 Organic Lab Data Collection Part I ? Alkanes 1. Volatility of methane, hexane, and paraffin Substance Methane Hexane Paraffin wax Observations Colorless gas, with a smell of sweet burnt alcohol. Clear, colorless liquid. Alcoholic smell, light but pungent. White, oily (waxy) solid. Very malleable, odorless. 1. Solubility of hexane and paraffin in water Substance Hexane + water Paraffin wax + water Observations Hexane when shaken with water does not dissolve. We can tell so because even though both liquids are clear and colorless, we can see a clear line which distinguishes one liquid from the other. The hexane floats right above the water, never mixing, and we can see the line of separation. Paraffin wax when shaken with water also does not dissolve. Even when finely ground, the solid pieces of wax float throughout the liquid and eventually deposit on the bottom of the test tube, never mixing with the water. 1. Combustibility of methane, hexane, and paraffin wax Substance Methane Hexane Paraffin wax Observations When the lighted splint is inserted in the test tube filled with methane, the flame quickly extinguishes itself, with a small spurt of black smoke. Right after, water vapour coats the walls of the test tube. Therefore, combustion occurred, since the water vapour means that H2O and CO2 are produced as bi products. ...read more.

Middle

1. Combustibility of methane, hexane, and paraffin wax 1. Methane CH4 (g) + 2 O2 (g) ï CO2 (g) + 2 H2O(g) * 1. Hexane 2 C6H14 (aq) + 19 O2(g) ï 14 H2O(g) + 12 CO2 (g) * 1. Paraffin wax No combustion reaction occurred - paraffin only changes state: C20H42 (s) + heat ï C20H42 (l) Part II – Comparison of alkanes and alkenes 1. Reaction of the double bond 1. Hexane No addition reaction occurred Concentrated H2SO4(l) C6H14 (aq) + KMnO4 (aq) C6H14 (aq) + KMnO4 (aq) 1. Hexene Concentrated H2SO4(l) C6H12 (aq) + KMnO4 (aq) C3H6O2 (aq) + KMnO2 (aq) 1. Combustibility of hexane and hexene 1. Hexane 2 C6H14 (aq) + 19 O2(g) ï 14 H2O(g) + 12 CO2 (g) * 1. Hexene C6H12 (aq) + 9 O2 (g) ï 6 H2O(g) + 6 CO2 (g) * Part III – Alcohols and Carboxylic acids 1. Oxidation of ethanol reflux 3 CH3CH2OH(aq) + 2 K2Cr2O7 (aq) + 8 H2SO4 (aq) + heat 3 CHâCOOH(aq) + 2 Crâ(SOâ)â(aq) + 2 KâSOâ(aq) + 11 HâO(g) 1. Making esters concentrated H2SO4 CH3CH2OH(aq) + CH3COOH(aq) CH3COOCH2CH3 (aq) + H2O(g) * These reactions are written as complete combustions, but in reality they were incomplete conbustions, as we can tell from the soot (carbon) ...read more.

Conclusion

Therefore, the combustion of hexene requires more oxygen than that of hexane, since the amount of oxygen in the atmosphere remains more or less constant. Part III – Alcohols and Carboxylic acids 1. Oxidation of ethanol The oxidation of ethanol is an oxidation of a primary alcohol. The reaction can occur because all the reaction conditions are present: heat, the oxidizing agent (K2Cr2O7 ) and the catalyst (H2SO4). Therefore, the alcohol (CH3CH2OH) first will form an aldehyde through distilling (low ratio of oxidizing agent to alcohol) but then through reflux it will form a carboxyllic acid (CHâCOOH). We can notice the reaction occurring by observing the changes in the test tube. Initially yellow-orange, the solution then turns green. Also, we notice a change in scent, from a pungent alcoholic scent, to a sweeter, more pleasant smell. 1. Making esters A reaction occurs when the ethanol and the ethanoic acid, aided by the catalyst H2SO4 and heat, form an ester CH3COOCH2CH3 and water. Also here, the reaction only occurs because the reaction conditions were present: heat and catalyst H2SO4. We can notice the reaction occurring by observing the changes in the test tube. The color changes from a warmer color, to a colder, blue-green color. Also, we notice a change in scent, from a pungent alcoholic scent, very unpleasant, to a fruity, sweet and tangy smell like lemon pie. Indeed, esters are used as artificial flavouring, replicsting the smell of fruits. ...read more.

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