Lab Report on Hydrocarbons

Post Lab Report

Experiment #6 Hydrocarbons

Submitted by: Penelope L. Babon

Date Performed: March 27, 2017                                Date Submitted: April 2, 2017

1. Objectives

1. To develop the ability to detect various signs of chemical change
2. To observe how hydrocarbon types may be detected and differentiate from each other by means of simple chemical tests (test tube reactions)
3. To compare the reactivity of alkanes, alkenes, alkynes and aromatic hydrocarbons towards selected chemical reagents
4. To carry out the laboratory preparation of acetylene

1. Results 

Table 1. Solubility behavior

Table 2. Reaction with Bromine

Table 3. Reaction with Baeyer's Reagent

Table 4. Reaction with Ammoniacal AgNO3

Table 5. Preparation and testing of Acetylene Gas

1. Discussions

Solubility Behavior

Hydrocarbons are molecules that have little or no polarity because they do not contain electronegative atoms. They are soluble in solvents of low polarity. They are not soluble in water, which is very polar, because the water molecules attract each other strongly (and are not nearly as interested in attracting nonpolar molecules). That explains why hydrocarbons we have tested were all immiscible in water.

Hydrocarbons did not react with 10% NaOH because NaoH is polar and hydrocarbons are molecules that have little or no polarity also with . Thus, it is expected that all samples would give a negative result towards these solvents. It is also worth noticeable that cyclohexane and cyclohexene gave a positive result for H2SO4. Again, cyclohexane's reaction with these solvents are just a result of experimental error. On the other hand, reaction of Cyclohexene with  co1uld happen. Since  is a strong acid, it protonated first the alkene. This is followed by the formation of carbocation which was attacked by the hydrogen sulfate ion.[pic 1][pic 2][pic 3]

        Nevertheless, one of the solvents is the , a non-polar compound. And since the samples are hydrocarbon, that is, they also are non-polar, theoretical result would be positive. But then again, Cyclohexene and Toluene gave a negative result which are results of experimental error.[pic 4]

Halogenation: Reaction with Bromine [pic 5]

In bromine tests, bromine does not react with saturated hydrocarbons (alkanes) because alkanes contain only C-C bonds which cannot add bromine. The bromine solution is red; the product that has the bromine atoms attached to carbon is colorless. Thus a reaction has taken place when there is a loss of color from the bromine solution and a colorless solution remains. In the cyclohexene solution, the color of the bromine solution was only diluted to orange to light orange unless added with UV light where it resulted in Bromine slowly disappearing over time. Bromine can react with an alkane, but this reaction requires heat or ultraviolet light to be successful, and the reaction is a substitution, not an addition: a hydrogen is replaced by a bromine and hydrogen bromide is a by product.

[pic 6]

Since this reaction does not take place in the absence of ultraviolet light or heat, if bromine is added to an alkane under these conditions (room temperature and no sunlight or other source of uv) the reddish-brown color of bromine will persist.

Alkenes undergo an addition reaction with bromine. The double bond of an alkene becomes a single bond and one bromine atom becomes bonded to each of the carbons that had shared the double bond. No other product is formed; the alkene and bromine simply add together, which is why it’s called an addition reaction. Addition of the bromine solution to cyclohexene resulted to the disappearance of color of the bromine solution after each drop and agitation.