Chemistry Lecture Notes

Conversion of Fischer Projection to Chair/Ring Conformation

Process Overview

• Formation of Ring Structure
  • Last alcohol group attacks the aldehyde
  • Forms the anomeric carbon

Numbering Carbons in Ring Structure

1. Anomeric carbon
2. Relate to starting chain
3. Marking positions for groups in the ring

Positioning Alcohol Groups

• Alcohols on the left: top position
• Alcohols on the right: down position
• Example:
  • 2: down
  • 3: up
  • 4: down
  • 5: CH2OH up
• Anomeric carbon (position 1) can be either up or down

Example Problem

• Correct answer: Choice C (for position of alcohol groups)

Comparison of Alpha and Beta Anomers of D-Glucose

• Beta Anomer
  • Hydroxyl group on anomeric carbon is equatorial
  • Less non-bonded strain
  • Correct Answer: B

Shared Glycosidic Linkage Types

• Polysaccharides: Glycogen and Amylopectin
  • Both have alpha-1,4 and alpha-1,6 linkages
  • Distinction:
    • Cellulose: beta-1,4 linkages
    • Amylose: no alpha-1,6 linkages
  • Correct Answer: D

Digestibility of Polysaccharides

• Maltose vs. Cellubiose
  • Both contain glucose subunits
  • Only maltose digestible by humans
    • Cellubiose has beta glycosidic linkages
  • Correct Answer: Maltose

Reaction Example: Muto-Rotation

• Interconversion between Ring Structures
  • Change in position of alcohol groups (cis to trans)
  • Correct Answer: Muto-rotation (C)

Conclusion

• Recap of Key Points
• Encourage questions, comments, and further study
• Good wishes for future studies