The document discusses three topics: 1) The importance of geometric cis-trans isomerism in vision chemistry. A shift between geometric isomers of 11-cis-retinal causes a signal transduction when light hits the retina. 2) The bromine water test to identify double or triple bonds. The test involves observing if bromine water is decolorized by an alkene undergoing addition. 3) Hydrogenation of alkenes is important industrially. Hydrogenation makes alkenes and aromatics less toxic and reactive, and is used in processing vegetable oils derived from polyunsaturated fatty acids.

1. Tupaz, Ishi Pearl C. BMLS 1-E
LECTURE ASSIGNMENT 8
CHEMISTRY 1
1. Discuss the importance of geometric cis-trans isomerism in the chemistry of
vision.
 The shift from one geometric structure to one another turns out to have
profound chemical or biochemical significance. The chemistry of vision
provides an example. The retina is our light detector at the back of the
eye. It contains 11-cis -retinal, a compound derived from Vitamin A. When
light reaches the retina, the cis retinal compound rapidly flips into its the
trans-isomer, and the process gives out a signal to nerve cells and hence
to the brain.
2. What qualitative test is used to show the presence of double or triple bond in an
organic compound? Discuss briefly this test and show the chemical equation that
describes the reaction.
 A qualitative test, used to classify the functional groups of alkene or
alkane present in the compound, is the bromine water test. In the dark
state, alkene groups react with bromine water and undergo an additional
reaction to provide a decolorized solution. In the other hand, with bromine
water, alkane does not react and the colour of the bromine water remains
the same. The most common compounds to undergo bromine water
testing are enol, alkenes, aniline, glucose, phenols, and acetyl groups.
3. What is the industrial importance of hydrogenation reaction of an alkene?
 Hydrogenation is used to saturate alkenes and aromatics, making them
less toxic and reactive. Hydrogenation is also important in processing
vegetable oils because most vegetable oils are derived from
polyunsaturated fatty acids.