Organic Chemistry Lab 315

Fall, 2014

DUE DATES• Today

– At beginning of lab -- Crystallization Report & Product; Spectroscopy Problems Part I

– At end of lab -- copy of laboratory notebook pages for today's experiment

• Next Week– At beginning of lab – Unknown Identification Report– Be sure to see the lab web page link/Manual for

Unknown Identification Reports for special instructions– Spectroscopy Problems Part II problem # 1– Syllabus Correction for next week ”Extraction of Caffeine

: Delete “Experiment: pp. 85-89” and include “Technique 12”.

In Lab Today

• Learn to use the IR spectrometer• Learn to set up a simple distillation• Identification of an unknown liquid

compound– Boiling point from simple distillation– Refractive index (“consensus” room

temp. written on blackboard)– IR spectrum– Water solubility and density relative to

water

Simple Distillation

• Distillation is the process of vaporizing a liquid in a container, condensing the vapor, and collecting the condensate in another container.

• May be used to:– Purify a liquid from a minor amount of

impurity, either solid or liquid– Separate liquids with different boiling points– Obtain an approximate boiling point range

(physical property)

Simple Distillation

• Pure (or nearly so) Substance– Temperature remains constant during

distillation process so long as both vapor and liquid are present

• Mixture of Liquids with boiling point differences of < 100o:

– Temperature increases throughout process because composition of vapor changes continuously and separation is poor.

Simple Distillation Set-up

water in

water out

distilling flask

receiving flask

water condenser

distilling head

take-off adaptor

immersed in ice-water bath

I must approve your set-up before you begin heating your flask.

Note position of thermometer!

Plastic clamps can be used to secure non-heated joints

Notes on Distillation

• Remember to use boiling stones!

• Distilling flask must be securely attached by clamp jaws.

• Thermometer must be properly placed to record an accurate temperature. Be aware that thermometers might be inaccurate.

• Use an ice-water bath to cool the receiving flask.

Notes on Distillation

• Please have your apparatus completely assembled, with tubing properly attached and water flowing, before asking me to approve your set-up.

• May need to use Al foil around set-up to keep in the heat (especially for high-b.pt. compounds).

• Never leave a distillation unattended.

• Do not distill to dryness!

• Transfer distillate to clean, dry vial after distillation.

Simple Distillation Set-up

water in

water out

distilling flask

receiving flask

water condenser

distilling head

take-off adaptor

immersed in ice-water bath

The Boiling Point Range

Is when the liquid is boiling in the flask AND when the vapor is bathing the thermometer bulb .

Until the vapor is surrounding the thermometer bulb, you are only measuring room temperature.

Wait until the temperature rises significantly AND you see condensate dripping into the receiving flask.

Notes

• When you have finished determining the boiling point, you can then take an IR. – FIRST, write your name on the board to establish

priority order.

• While you are waiting to take an IR or after taking it, determine refractive index, water-solubility and relative density of unknown.– We will use one room temperature reading for all

the class.

– See Pavia p. 454-455 for water-solubility and relative density.

Lab Clean-up

• Fenton

• Trinh