phys/chem properties (MIDTERM REVIEW)

what are the components of honey?

• water

• glucose

• minerals

• proteins

• beeswax/pollen

what does lugol’s test for? and how does it work?

the presence of starch, when starch is present the iodine in the reagent binds and the color changes as a result of an exchange of electrons between the reagent and sample.

how would you know the results of lugol’s test

negative (no starch)= honey color; positive(starch)=black

what does benedict’s test for? and how does it work?

test for amount of reducing sugars; a reducing sugar is subjected to heat in the presence of an alkali, it gets converted into a reducing agent. So when reducing sugars are present in the sample, the ions in Benedict’s reagent are reduced, changing the color.

how would you know the results of benedict’s test

range from blue (no reducing sugar) to red( high reducing sugar)

what does tollen’s test for? and how does it work?

tests for aldehydes; tollen’s reagent oxidizes the aldehyde, during this process silver ions in the reagent are reduced to metallic silver

how would you know the results of tollen’s test

negative (no aldehydes) - no silver / positive (yes aldehydes ) - yes silver/mirror effect

what does seliwanoff’s test for? and how does it work?

tests for ketones; turns this color after heating due to the fact that the ketones present in the sample will dehydrate faster than the aldoses present.

how would you know the results of seliwanoff’s test

negative (no ketones) - clear / positive (yes ketones) red/pink color

what does bial’s test for? and how does it work?

test is used to distinguish between pentoses and hexoses, and as such the light yellow color is the result of the chemical mixture not reacting with pentose sugars in a way that produces a distinct color change

how would you know the results of bial’s test

negative(no pentoses) light green or orange color - positive( yes pentoses) blue color

what does biuret’s test for? and how does it work?

test is used to detect the presence of peptide bonds in the sample and to test for the presence of proteins or peptides; intensity of the color produced by this test is directly proportional to the protein concentration, which explains how despite containing protein the honey could remain the same color

how would you know the results of bial’s test

positive(yes proteins) - purple color/ negative(no proteins) - blue color

what is a reducing sugar?

carbohydrates with free aldehyde or ketone groups that can be oxidized.

what is a pentose?

Monosaccharides w 5 carbon atoms

what is a hexose?

Monosaccharides w 6 carbon atoms

aldoses

carbohydrates with an aldehyde group

ketoses

carbohydrates with a ketone group

carbonyl group

carbon double bonded to a oxygen atom

Monosaccharides

simple sugars and can have anywhere from 3-9 carbon atoms

what bonds w this molecule?

aldehyde - In Tollens reagent, the component that reacts with aldehydes is the silver ion (Ag+) complexed with ammonia (Ag(NH3)2+)

what bonds w this molecule?

ketone - Seliwanoff's reagent contains a non-oxidizing acid (HCl). When a ketose is reacted with this reagent, it becomes dehydrated and a cherry-red color forms.