Biomolecules Flashcards
What are carbohydrates?
Carbohydrates are polyhydroxy compounds containing aldehydes or ketones containing at least one asymmetric c-atom with formula Cx(H2O)y
Monosaccharides
Simplest carbohydrates which will not undergo hydrolysis
Glucose and fructose are _____
Monosaccharides
Oligosaccharides
Are carbohydrates which one hydrolysis give 2-10 simpler sugar units
Examples of oligosaccharides
Sucrose, maltose, lactose and raffinose
Polysaccharides
Are carbohydrates which one hydrolysis give large no: of simpler sugar units
Examples of polysaccharides
Starch, cellulose
Glucose on reaction with tollen’s reagent gives…
Gluconic acid and Ag (silver mirror)
(CHO –> COOH)
Glucose on reaction with Fehlings reagent gives…
Gluconic acid and Cu2O (red ppt)
(CHO –> COOH)
Glucose on reaction with Bromine water gives…
Gluconic acid
(CHO –> COOH)
How can we obtain gluconic acid?
When glucose is treated with mild oxidising agents like tollen’s, Fehlings and bromine water gluconic acid is obtained.
(CHO –> COOH)
What happens when glucose is treated with strong oxidising agents like conc HNO3?
Saccharic acid or glucaric acid is obtained
(Aldehyde and 1° alcohol oxidised to COOH)
Name the compound:
COOH
|
H-C-OH
|
HO-C-H
|
H-C-OH
|
H-C-OH
|
COOH
Saccharic acid or glucaric acid
Name the compound:
CHO
|
H-C-OH
|
HO-C-H
|
H-C-OH
|
H-C-OH
|
CH2OH
Glucose
Name the compound:
COOH
|
H-C-OH
|
HO-C-H
|
H-C-OH
|
H-C-OH
|
CH2OH
Gluconic acid
Name the compound:
CHO
|
H-C-OCOCH3
| OCOCH3-C-H
|
H-C-OCOCH3
|
H-C-OCOCH3
|
CH2OCOCH3
Penta acetyl ester
What happens when glucose is treated with hydroxylamine?
Corresponding oxine will be obtained (aldehyde will undergo condensation)
(CHO –> CH=N-OH)
What happens when glucose is treated with HCN?
It undergoes nucleophilic addition to form cyanohydrin
OH
/ (CHO --> CH )
\
CN
What happens when glucose is treated with HI
n-Hexane is obtained
(This rqn proves that glucose contains y carbons without branching)
Why does glucose exist as a cyclic structure?
Due to rqn b/w OH and CHO group
Why does glucose exist as a cyclic structure?
Due to rqn b/w OH and CHO group
What are α and β D(+) glucose?
α and β forms are anomers.
These are two forms of glucose which differ in the arrangement of H and OH on the first carbon
Even though glucose contains an aldehyde group it failed to answer reaction with NaHSO3 and Schiffs reagent. Why?
Becuz glucose does not exist as an open structure with free CHO group. Instead it exist as α and β form
Melting point of α D (+) glucose
419K
