Chapter 13 Carbohydrates 1 13 3 Haworth Structures

Chapter 13 Carbohydrates 1 13. 3 Haworth Structures of Monosaccharides Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Cyclic Structures 2 Cyclic structures • are the prevalent form of monosaccharides with five or six carbon atoms • form when the hydroxyl group on carbon 5 reacts with the aldehyde group or ketone group Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Guide for Drawing Hayworth Structures 3 Chemistry: An Introduction to General, Organic, and Biological

Drawing the Cyclic Structure for Glucose 4 Step 1 Number the carbon chain and turn clockwise to form a linear open chain. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Drawing the Cyclic Structure for Glucose 5 Step 2 Fold clockwise to make a hexagon. • Bond the carbon 5 –O– to carbon 1. • Place the carbon 6 group above the ring. • Write the –OH groups on carbon 2 and 4 below the ring. • Write the –OH group on carbon 3 above the ring. • Write a new –OH on carbon 1. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Drawing the Cyclic Structure for Glucose 6 Chemistry: An Introduction to General, Organic, and

Drawing the Cyclic Structure for Glucose 7 Step 3 Write the new –OH on carbon 1 down for the form and up for the form. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Mutarotation of -D-Glucose and β-D-Glucose in Solution 8 When placed in solution, • cyclic structures open and close • -D-glucose converts to β-D-glucose and vice versa • at any time, only a small amount of open chain forms CH 2 OH OH (36%) O O C H OH D-Glucose (open) (trace) Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition OH OH -D-Glucose H O OH CH 2 OH OH β-D-Glucose (64%) Copyright © 2012 by Pearson Education, Inc.

Cyclic Structure of Fructose 9 Fructose • is a ketohexose • forms a cyclic structure • reacts the —OH on carbon 5 with the C=O on carbon 2 CH 2 OH C O CH 2 OH HO C H CH 2 OH O OH H C OH CH 2 OH OH CH 2 OH D-Fructose α-D-Fructose Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition -D-Fructose Copyright © 2012 by Pearson Education, Inc.

Learning Check 10 Write the cyclic forms of D-galactose. Chemistry: An Introduction to General,

Solution 11 Step 1 Number the carbon chain and turn clockwise to form a linear open chain. 1 2 3 6 5 4 3 2 1 4 5 6 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution 12 Step 2 Fold clockwise to make a hexagon. • • • Bond the carbon 5 O to carbon 1 and change the =O to OH on carbon 1. Place the carbon 6 group above the ring. Write the OH groups on carbon 2 and carbon 4 below the ring and the OH group on carbon 3 above the ring. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution 13 Step 3 Write the new –OH on carbon 1 down for the form or up for the form. -D-Galactose Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition -D-Galactose Copyright © 2012 by Pearson Education, Inc.