Lab Report Questions

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LabReport Questions


1.The wavelength of maximum absorption of spinach was for tomatopaste was 469.0nm at 340nm whereas that of spinach was 449.0nm at340nm.

2.Spinach contains beta carotene whereas tomato paste containslycopene pigments.

3.Both carotenoids are hydrocarbons, and they are made of carbonsand hydrogen. The chemical structures are as follows:

Figure1: Chemical structure of lycopene

Figure2: Chemical structure of beta-carotene

4.Structure of cis rubber is as follows

5.Structure of trans-natural rubber is as follows

6.Cis and trans rubber differ in their properties as follows cisisomer is easily stretched and mere elastic, unlike the trans rubberwhich is harder. Despite the fact that both isomers are made ofisoprene units, their properties are due to their differinggeometries. The trans isomer can be tightly packed into one anotherwhile cis isomer cannot. Therefore the cis isomer has fewer crosslinkages as compared to Trans isomer making it more elastic.

7.Yes. I would expect the polymers to be biodegradable since theycan be acted upon by microorganisms which

8.Example of biodegradable polymer is Polyhydroxy butyrate (PHB)

9.Example of nonbiodegradable polymer is polyethylene

10.Rubber bands are made of natural which is obtained from latex orsynthetic rubber which has been chemically modified initially, itwas made of vulcanized rubber.

11.Deterioration of rubber is due to the breakage of the C-H or C-Cbonds due to the presence of impurities and environmental stress.Free radicals are produced as a result which reacts with oxygen toform hydrogen peroxide causing further polymer chain breakage.Reaction responsible for the deterioration of rubber is as follows

12.Rubber bands can be preserved to last for a long time by sealingthe rubber bands in a container where there is minimal exposure tooxygen and water vapor. They should also be kept in cold conditionsbelow 250 C to avoid deterioration.

13.The tomato paste did not undergo column chromatography becauselycopene in tomatoes also has a lower RF value as compared to betacarotene in column chromatography. Because lycopene is less polarthan beta-carotene, therefore, more soluble and weakly adsorbed tothe chromatographic column. Lycopene is strongly adsorbed to thecolumn thereby requiring stronger solutions for elution which wouldotherwise destroy the pigment. The reflux provided enough agitationand energy of the reaction through stretching and bending of bondswhich were directly detected by a spectrophotometer.

14.Lycopene and carotenoids are colored hydrocarbons because they arederivatives of 8 isoprene units, that is, tetraterpenes and contain40 carbon atoms which are conjugated.

15.Yes, it is possible for all-trans lycopene to transform to 7-cislycopene in the presence of a catalyst. Structure of 7 cis-lycopeneis as follows


a.Numbers involving isoprene units – 7,8 and 9

b.Numbers containing an epoxide – 7,9 and 10

c.Styrene oxide is an epoxide derived because it has an oxygen atomattached to two carbon atoms which are characteristic of epoxides.

Chemicalstructure of styrene oxide is

d.The functional group of figure 7 and 8 is a ketone. Simplestexample of the group is a propanone

Thefunctional group is given by

17.a) Chemical structure of flavylium ion

b)Reaction of flavylium cation from red to blue (Quinoidal base) whenreacted with Al+3or Fe+3.

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