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Lecture 29. Hand in Lecture Problem 10 Sweeteners Quiz 8 on Thursday in lecture This Week in Lab: Synthetic #2 Final Report; Lab Clean-up & Check-out! Remember to bring all graded PreLabs and Aldrich to lab. Sweeteners. Carbohydrates: Mono- and disaccharides Examples:

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slide1

Lecture 29

  • Hand in Lecture Problem 10
  • Sweeteners
  • Quiz 8 on Thursday in lecture
  • This Week in Lab:
  • Synthetic #2 Final Report; Lab Clean-up & Check-out!
  • Remember to bring all graded PreLabs and Aldrich to lab.
slide2

Sweeteners

Carbohydrates:

Mono- and disaccharides

Examples:

Sugar, corn syrup, maple syrup, juice concentrates

slide3

Saccharin

  • Non-carbohydrate sweetener
  • Sweet’N Low, Sugar Twin
  • Discovery Story:
  • In 1879 by Constantine Fahlberg
  • By 1907, saccharin was used by diabetics
  • Not metabolized in the body for energy
  • By 1960’s, used in diet soft drinks
  • Safety controversy due to findings of bladder tumors
  • in some male rats
  • More than 30 human studies conclude that it’s safe
slide4

Saccharin

Sweetness:

Shape must fit into specific

receptors in taste buds.

When shape is slightly modified, it is no longer

sweet:

slide5

Aspartame

  • Non-carbohydrate sweetener
  • Equal, NutraSweet

Aspartame

slide6

Aspartame

  • Discovery story:
  • In 1965 by Jim Schlatter
  • working on discovering new
  • treatments for gastric
  • ulcers.
  • Made a dipeptide intermediate,
  • which he spilled on his hand
  • Tested the dipeptide in coffee

Aspartame

  • 4 calories per gram
  • 180 times sweeter than sugar
slide7

Aspartame

Aspartame is metabolized in the body into:

methanol (wood alcohol), phenylalanine, and aspartic acid

Phenylalanine is an essential amino acid and is a

precursor for the synthesis of tyrosine and several

neurotransmitters.

Excess phenylalanine is broken down into

fumarate and acetoacetate - normal energy metabolism.

slide8

Aspartame

Safety concerns:

If lacking the enzyme to convert

phenylalanine to tyrosine, have

phenylketonuria, PKU.

Phenylalanine is then converted to phenylketones instead.

PKU could lead to mental retardation if not detected or treated.

Aspartame

Products that contain aspartame carry an information

label for phenylketonurics.

slide9

Aspartame

Safety concerns:

Reports of formaldehyde

poisoning.

Methanol quickly converts to

formaldehyde in the body.

Formaldehyde causes severe damage to the neurological system, immune system, and causes permanent genetic damage at extremely low doses.

Aspartame

slide10

Aspartame Synthesis

Two main constituents:

Phenylalanine

Aspartic acid

Goal:

Make the methyl

ester of phenylalanine

2. Make a peptide (amide)

bond between phenylalanine

and aspartic acid

Overall - two main steps to this synthesis

slide11

Aspartame: Ester Synthesis

Only the S enantiomer of phenylalanine is desired for use. The R and

S enantiomers can be separated before the esterification reaction.

slide13

Sucralose/Splenda

  • Carbohydrate-based sweetener
  • Made from sugar
  • 600 times sweeter than sugar
slide14

Sucralose/Splenda

  • Does not metabolize to produce energy, thus no calories
  • Only low calorie sweetener made from sugar
  • Heat stable - used in cooking and
  • baking
  • Discovery story:
  • In 1976 by Dr. Hough’s lab
  • at King’s College
  • From 1980 onwards, collaboration
  • with Tate & Lyle, a British sugar company,
  • and McNeil Specialty Products
slide15

Quiz 8

  • Reactions:
  • Electrophilic Aromatic Substitution Reactions:
  • Nitration
  • Friedel Crafts Alkylation & Acylation
  • Substitution Reactions:
  • Williamson Ether Synthesis
  • Elimination Reactions:
  • Dehydration of alcohols
  • Oxidation:
  • Epoxidation of alkenes
  • Of alcohols
  • Of benzylic carbons
  • Reduction:
  • Of alkenes
  • Of carbonyls
  • Esterification:
  • Fisher
  • Alternative (with anhydrides)
  • Enolate Chemistry:
  • Adol & Aldol Condensation
  • Mixed Aldol
slide16

Quiz 8

  • Reactions:
  • Be able to draw out the mechanisms of only those
  • reactions that were given in lecture. Know the reagents
  • used for each reaction.
  • Special topics:
  • Drug candidates
  • Drug discovery process
  • Retrosynthetic analysis
  • Molecular modification
  • Sweeteners
  • Be able to identify a compound
slide18

Practice Quiz Problems

Design a synthesis of the following ester. You can use

either the Fisher esterification method or the

alternative esterification method. Give the overall

reaction equation with starting materials, reagents, and

main organic product.