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

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Cyclic Structures 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 2

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

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Drawing the Cyclic Structure for Glucose 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. 5

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 Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. 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 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  - D -Glucose D -Glucose (open) β - D -Glucose (36%) (trace) (64%) 8 O H CH 2 OH OH O C H OH OH OH OH OH OH CH 2 OH O OH OH OH OH CH 2 OH O

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

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check Write the cyclic forms of D-galactose. 10

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 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. Solution 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. 12

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