Carbohydrate Chemistry (5/13)

Question 1

Anomers

Answer 1

Carbohydrate isomers that differ in their orientation of their substituents at the anomeric carbon (mainly the hydroxyl group)

Question 2

The anomeric carbon

Answer 2

The carbon with the double bond to oxygen in its linear form. It is a solid electrophile making it a promising site for nucleophilic attack

Question 3

When aldose cyclizes

Answer 3

Forms a hemiacetal

Question 4

When a ketose cyclizes

Answer 4

Forms a hemikatal (instead of a second bound to oxygen, it forms a bond with another R-group

Question 5

If hydroxyl attacks from carbon 4

Answer 5

Intermolecular attack to form a furanose

Question 6

If hydroxyl attacks from carbon 5

Answer 6

Intermolecular attack to form a pyranose

Question 7

When hydroxyl group points up

Answer 7

beta

Question 8

When hydroxyl group points downwards

Answer 8

alpha

Question 9

Mutarotation

Answer 9

alpha and beta can rapidly convert back and fourth

Question 10

Glycosidic bonds

Answer 10

dehydration reaction

Question 11

Glycosidic bond hydrolysis

Answer 11

Hydration event. Water comes in and attaches, then is deprotonated to restore hydroxyl group

Question 12

Maillard reaction

Answer 12

occurs between 140-165 degrees C
amino acids in foods are reacting with certain carbohydrates
happens faster under basic conditions

Question 13

Reducing sugars

Answer 13

undergo a redox reactions and therefore lose electrons to become oxidized
EX)
aldehydes, non-aldose sugars that can be converted into aldoses, maltose and lactose (because they have a free anomeric carbon)

Question 14

If apart of a glycosidic bond…

Answer 14

Cannot participate in a redox reaction

Question 15

Metals that usually carry out redox reactions

Answer 15

Act as oxidizing agents:

Cu, Ag, Fe

Question 16

Tollen’s test

Answer 16

When aqueous silver is added to a sugar and then forms a solid. Once it precipitates from a solution, it produces a visible silver film that looks like a mirror

Question 17

Benedict’s test

Answer 17

When aqueous copper is added to sugar the solution start blue and if aldehyde is present, turns solution red

Question 18

Fehling’s test

Answer 18

Adding aqueous copper to sugar and measured the amount of oxidizing agent (CuO)

Question 19

Sugar chemistry for the Maillard reaction

Answer 19

All monosaccharides are reducing agents
All ketoses tautomerize to aldoses and all aldoses are reducing agents
Disaccharides are reducing agents if they have a free anomeric carbon
Polysaccharides are usually non-reducing agents