Download The Synthesis of Fragrance Compounds: Corn-Chip

CRITICAT CDT
The Synthesis of Fragrance Compounds:
Corn-Chip Aroma
Disclaimer for Experimental Work
The procedure described within must be conducted at one's own risk. St Andrews University and
affiliates do not warrant or guarantee the safety of individuals using these procedures and hereby
disclaim any liability for any injuries or damages claimed to have resulted from or related in any way
to the procedures herein.
An appropriate risk assessment must be conducted before hazardous materials are used or
hazardous procedures undertaken. This is the responsibility of the employer and users of resources
involving a practical activity to review and comply with the appropriate risk assessment supplied by
the employer.
CRITICAT CDT
Introduction: In this short classroom demonstration we will create a potent fragrance compound.
The product formed has a distinct aroma of corn chips, however, a number of people identify the
smell as buttered popcorn. The demonstration involves the reaction of 2,3-butanedione (1),
methylamine hydrochloride (2) and a base (5M NaOH) to form 3-methylimino-2-butanone (3) as
shown below:
Imine 3 has been patented as a flavouring agent for foodstuffs and is proposed to act as a mimic of
2-acetyl-1-pyrolline (4) which is associated with the pleasant odour of cereal products.
Connections to the Syllabus: The formation of imine 3 is an example of a condensation reaction and
can be used to introduce ester synthesis, another class of condensation reaction that forms
fragrance compounds. The experiment could also be used to discuss the reactivity of ketones (and
aldehydes) with amines.
Experimental Procedure:
2,3-Butadione (0.43g, 5 mmol) and methylamine hydrochloride (0.33g, 5 mmol) were placed in a test
tube with a stopper. When you are ready to form the aroma, the stopper is removed and a mixture
of ethanol (1 mL) and 5M NaOH (1 mL) is added slowly. An immediate colour change from yellow to
brown/black is observed along with the evolution of heat. The stopper is replaced and gently shaken
for one minute before the stopper is removed to allow the audience to detect the aroma.
Safety and Waste Disposal:
Safety and waste disposal information can be found in the SSERC risk assessment below
References:
This experimental procedure was originally reported by A. T. Sartori and W. F. Wood; J. Chem. Educ.,
1992, 69, 572.
SSERC Risk Assessment (revised version November 2009)
(based on HSE ‘5 steps to risk assessment’)
2 Pitreavie Court, South Pitreavie Business Park, Dunfermline KY11 8UB
tel : 01383 626070 fax : 01383 842793
e-mail : [email protected] web : www.sserc.org.uk
Activity assessed
Date of assessment
Date of review (Step 5)
School
Department
Step 1
Preparing a Schiff base
23rd June 2016
Step 2
Step 3
List Significant hazards
here:
Who might be harmed
and how?
What are you already doing?
2,3-butadione is
Flammable (Cat 2) Causes
eye damage (Cat 1) and is
a skin irritant and
sensitiser. It is also toxic if
inhaled (Cat 3) and
repeated exposure can
cause respiratory damage
Methylamine hydrochloride
is a skin, eye and
respiratory irritant and is
harmful if ingested.
Industrial denatured
alcohol (IDA) is highly
flammable
5M sodium hydroxide is
highly corrosive
Technician or
demonstrator, preparing
the reaction mixture by
splashing or inhalation
Use a fume cupboard.
Keep away from sources of
ignition
Wear goggles (BS EN 133 3)
and gloves.
Technician or
demonstrator, preparing
the reaction mixture by
splashing or inhalation
Technician or
Demonstrator by burns
Work in a well-ventilated room.
Wear eye protection (and gloves
if preferred)
Technician or
Demonstrator by burns
What further action is needed?
Wear eye protection
Keep container well away from
any sources of ignition.
Wear goggles (BS EN 133 3)
and gloves.
The product, 3methylimino-2-butanone, is
of low hazard
SSERC
1
2009
Step 4
Action
by
whom?
Action
by
when?
Done
Description of activity:
A mixture of 0.43 g 2,3 butadione and 0.33 g of methylamine hydrochloride is mixed in a test tube and stoppered.
For the demonstration, 2cm3 of a 1:1 mixture of ethanol and 5M sodium hydroxide is slowly added to the tube, the stopper is replaced and the mixture gently
shaken for a minute.
The audience is then allowed to smell the product.
Additional comments:
The butadione/methylamine hydrochloride mixture is best prepared in a fume cupboard.
The small quantities of butadione and methylamine hydrochloride minimise the risk and there seems no reason to scale this demonstration up.
Disposal
The reaction mixture can be poured into a solution of ethanoic acid (or another weak acid) to neutralise the strong alkali and then washed to waste with
plenty of cold running water.
SSERC
2
2009