Post Lab Report
Hayley Peerless
Experiment 3: Steam Distillation of Spices
November 4th, 2014

Results

Table 1. Results

Spice
Crude Mass (g)
Primary Flavoring Component Recovery (%)
Distillation BP (°C)
Cumin
4.43
0.456
100

Table 2. IR Spectral Data

Chemical Structure and Name
Exp. Peaks (cm-1)
Lit. Peaks (cm-1)
Intensity
Functional Group/Bonding

Cuminaldehyde
~3400
2900-3000
1715
~1500
~3400
2900-3000
1703
1462-1576
M
S
S
S
Sp Hybridization str.
Sp3 Str, and aldehyde doublet
C=O Str.
Aromatic ring Str.

Sample Calculations

Percent Recovery of Essential Oil

Discussion

The purpose of this laboratory experiment was to steam distill a specific spice (cumin in this particular case) with intent of isolating and recovering the primary flavoring component, Cuminaldehyde. These essential oils are predominantly composed of monterpene compounds that normally require high distillation temperatures or reduced pressure, however there are some aspects of boiling points that can be used in favor of the experiment. This idea can be represented by the analogy “Mixtures of immiscible liquids exhibit depressed boiling points in a manner analogous to mixtures of solids giving low melting points”i; although not completely insightful about the physics behind the reaction, it provides a simple reasoning for the overall concept.

For Part A of the experiment – Steam distillation – the general procedural steps of weighing, assembling apparatus and boiling were crucial in terms of precision and accuracy in order to yield the maximum amount of Cuminaldehyde. The round bottom flask, or RBF, was weighed using an analytical scale to ensure accuracy; measurements were taken for both the crude weight of the flask as well as the flask containing the spice and stir bar. Assembling the simple steam distillation apparatus properly was also of significant importance because if it were connected improperly it could have resulted in a water leak, loss of steam and invalid (or absent) yield of the flavoring component. In addition, after initial assembly, it was also important that the large RBF containing the dissolved spice be wrapped in aluminum foil to ensure heat retention, thus allowing the system to reach a boiling point of 100°C, without the input of an external heat source (Although originally stated to be boiled with the use of a heating mantle & hot plate, the system was self-sustaining and the apparatus were simply used to control the rate of stirring).

For part B of the experiment – Isolation – precision and accuracy were crucial as the minimal yield of pure Cuminaldehyde could have been compromised, resulting in the loss of all of the product. Following the part A, the distillate was cooled and transferred to a separatory funnel, in which dichloromethane was used to create the two layers. During this section of the procedure it was important that the funnel inverted and subsequently released of all vapors that resulted from emulsion. Furthermore, after draining the DCM layer into a separate and clean Erlenmeyer flask, it was crucial that the solution was properly and correctly dried using anhydrous Magnesium sulfate (MgSO4), this was to ensure that the final yield was pure Cuminaldehyde. The final step of the procedure, excluding the IR spectral data collection step, was to remove the solvent using the rotary evaporator (RotoVap). This was a important step because if done insufficiently or incorrectly it would result in abnormal or lack of proper peaks in the IR spectral data analysis leading to an invalid conclusion/experiment.

Based on the spectral data analysis on the primary flavoring component that was isolated, which shows significant peaks at ~3400, 2900-3000, 1715 and ~1500, the overall structure must contain a benzene ring with a no-conjugated aldehyde. This is because the peaks in the range of 3400 likely indicate there is sp hybridization present, which coincides with the non-conjugated aldehyde (given by the