Qualitative Tests of Carbohydrates

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QUALITATIVE TESTS OF CARBOHYDRATES
Final Lab Report

Submitted by

Brittany Fitzgerald
545301

Prepared for

Nancy Cook
Chemistry 3501
Monday

November 26, 2012

RESULTS
PART A:
As a result of the Benedict’s test on various sugar solutions, it was found that galactose, mannose, arabinose, ribose, lactose, fructose, maltose, and cellobiose tested positively and therefore are considered reducing sugars. Glucose, starch, sucrose, and methyl-D-glucopyranoside on the other hand tested negatively and therefore are considered non-reducing sugars.
Table 1. Results of Benedict’s test on various sugar solutions Sugar Solution | Color | Clarity | Glucose | Bright blue with orange tint on top | Clear | Galactose | Brown on top, blue-ish on bottom | Opaque | Mannose | Brown on top and bottom, green/blue in middle | Opaque | Arabinose | Brown/copper on top, blue/green on bottom | Opaque | Ribose | Brown/green throughout | Opaque | Lactose | Brown on top and bottom, blue-ish in middle | Opaque | Fructose | Brown/green throughout, red on bottom | Opaque | Maltose | Green/blue throughout, red on bottom | Opaque | Cellobiose | Green/blue through, red on bottom | Opaque | Starch | Bright blue | Clear | Sucrose | Bright blue | Clear | Methyl-D-glucopyranoside | Bright blue | Clear |

PART B:
As a result of the Seliwanoff’s test on various carbohydrates, it was found that only fructose and sucrose tested positively and therefore they are considered ketoses.

Table 2. Results of Seliwanoff’s test after 1 minute Carbohydrate/Water | Color | Glucose | Colorless | Fructose | Colorless | Sucrose | Colorless | Water | Colorless |

Table 3. Results of Seliwanoff’s test after 2 minutes Carbohydrate/Water | Color | Glucose | Colorless | Fructose | Light pink/red | Sucrose | Colorless | Water | Colorless |

Table 4. Results of Seliwanoff’s test after 3 minutes



References: Eaton, David C. 1989. “Experiment 33: Carbohydrates.” Accessed November 17. http://moodlelive.msvu.ca/file.php/5622/Carbohydrates.pdf Mount Saint Vincent University. 2012. “Chemistry 3501 Lab Manual”. Nova Scotia: Halifax. Schreck, James O., Loffredo, William M. 2012. “Qualitative Testing for Carbohydrates.” Accessed November 16. http://kurdchemists.org/files/carbohydrates%20test%20new.pdf

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