Exp 6.4: Lipids (Quali Tests)

Question 1

Hydroxamic Test:
purpose

Answer 1

Detect presence of carboxylic acid ester (glycerophospholipids, TAGs, cholesteryl esters)

Question 2

Hydroxamic Test:
reagents

Answer 2

ethanol:butanol(3:1)
NH2OH x HCl
NaOH
FeCl3
HCl

Question 3

Hydroxamic Test:
positive result

Answer 3

Burgundy color

Question 4

Hydroxamic Test:
principle

Answer 4

Complexation Reaction

Question 5

Acrolein Test:
purpose

Answer 5

Detect presence of glycerol (glycerophospholipids, TAGs,)

Question 6

Acrolein Test:
positive result

Answer 6

Burnt fat odor

Question 6

Acrolein Test:
reagents

Answer 6

KHSO4
water bath

Question 7

Acrolein Test:
principle

Answer 7

Dehydration and oxidation

Question 8

Libermann-Burchard Test:
purpose

Answer 8

Detect presence of unsaturated sterols (cholesterol)

Question 9

Libermann-Burchard Test:
reagents

Answer 9

Conc. H2SO4
acetic anhydride

Question 10

Libermann-Burchard Test:
positive result

Answer 10

Emerald green solution

Question 11

Libermann-Burchard Test:
principle

Answer 11

Esterification of OH at C- 3 with acetic anhydride
Epimerization of double bond at C-5

Question 12

Kraut’s Test:
purpose

Answer 12

Detect presence of choline (phosphatidyl choline, sphingolipids)

Question 13

Kraut’s Test:
reagents

Answer 13

Bismuth nitraye
3M HNO3
KI (Kraut’s reagent)

Question 14

Kraut’s Test:
positive result

Answer 14

Dark orange to red ppt

Question 15

Kraut’s Test:
principle

Answer 15

Complexation reaction
● proposed condensation, dehydration & epimerization
● modification of Dragendorff’s test

Question 16

Ascorbic Acid Method:
purpose

Answer 16

Detect presence of phosphate (phospholipids)

Question 17

Ascorbic Acid Method:
reagents

Answer 17

6M HNO3
6M NaOH
Molybdate Rgt
0.1M Ascorbic Acid Solution

Question 18

Ascorbic Acid Method:
positive result

Answer 18

reduced to intensely colored molybdenum blue by ascorbic acid

Question 19

Ascorbic Acid Method:
principle

Answer 19

Ammonium molybbdate + potassium antimonyl tartrate react in acid medium with orthophosphate = heteropoly acid to phosphomolybdic acid

Question 20

Ninhydrin Test:
purpose

Answer 20

Detect presence of α-amino group

Question 21

Ninhydrin Test:
reagents

Answer 21

Triketohydrindene hydrate (ninhydrin in EtOH)

Question 22

Ninhydrin Test:
positive result

Answer 22

Blue-violet solution

Question 23

Ninhydrin Test:
principle

Answer 23

Oxidative deamination followed by condensation

Question 24

Test for Lipid Unsaturation:
purpose

Answer 24

Detect presence of double bonds; degree of unsaturation

Question 25

Test for Lipid Unsaturation:
reagents

Answer 25

5% Bromine / Iodine solution

Question 26

Test for Lipid Unsaturation:
positive result

Answer 26

Reddish brown
Violet coloration

Question 27

Test for Lipid Unsaturation:
principle

Answer 27

Addition reaction

Question 28

Molisch Test:
purpose

Answer 28

Detect presence of sugar moiety

Question 29

Molisch Test:
reagents

Answer 29

1% ethanolic α- napthol, conc. H2SO4

Question 30

Molisch Test:
positive result

Answer 30

Violet ring at the interface

Question 31

Molisch Test:
principle

Answer 31

Hydrolysis, dehydration, and condensation reaction