Tested Overhead Projection Series Compiled by HUBERT N. ALYEA Princeton University

22. ORGANIC CHEMISTRY

A. General Dem. 6 6 1-Ammonium Cyanaie fram Urea

To show; Formation of ammonium and cyanate ions by heating urea-aq; a reversal of the classical Wohler's synthesis:

(NH)&=O ~1 NIL,+ + OCN- urea rtrnmo~uum eyanate

Materials: 1 molar urea, device E-1 or Me-amps for measuring current.

Procedure: (a) Project two culture tubes half-filled with 1 M urea in H-3. Boil tube B for 5 min. Now transfer the tubes to Me-amps, project, and test for conductivity. (b) Ditto, but add two drops of AgN03- aq to each.

Observations: (a) The unboiled tuhe (urea) does not conduct; the boiled tuhe (NH,+ and OCN-) conducts. (b) Tube 1, no reaction with Ag+; tube 8 precipitates white (macro) AgOCN.

Reference: WALKER, J., and HAMBLEY, 13. J., J. Chem. Soc., 87, 746 (1894); SCHEER, R., P rmis Chem., 5, 56 (1956); SEETHAHAMAN, P. A,, J. Chem. Igduc., 39, A8.19, 1962 uses urea which reverts to ammonium cyanate.

B. Chain Compounds Dem. 662-Amylene + Bramine

To shoto: The addition of bromine to unsaturated hydrocarbons.

Material: Bromine, amylene (I-pentene), H-3, cotton.

Procedure: Project two culture tubes in H-3. Tilt an unstoppered bottle of bromine over each, so as to fill them with the reddish-brown vapor; then quickly stopper them with small plugs of cotton. Now put two drops of amylene into tube 2, stopper it again.

Observations: Tube 2 becomes colorless as the bromine in i t adds to the unsaturated bond in amylene.

Reaction: CHFCH-CH1-CH,-CH3 + Br, - CH2Br-CHBr-CH1-CH3-CH3

Dem. 663-Cracking Mineral Oil

Experiment developed by Ken.neth V. Jaclcman.

To sh,ow: The cracking of mineral oil, using Fe as catalyst, to give unsaturates which add bromine.

Materials: Steel wool, H-3, mineral oil, dropper, bromine.

Procedure: Push a loose wad of steel wool into the bottom half-inch of a culture tube, and to this add four drops of mineral oil. Project in H-3. Heat until white clouds (hydrocarbons) appear. Now tilt an unstoppered bottle of Brs to let the reddish-brown vapor spill into the culture tuhe. Immediately stopper. Let stand a few seconds.

Observations: The reddish-brown color disappears. Reason: The steel wool catalyzes the crackiug of the hot oil, giving unsaturated products; the double bonds in the latter add bromine which disappears.

A Bn Reactions: CnHzn+z 7 CCnHzn C,H&b

Dem. 664-Cracking Bacon Fai

To show: The high-temperature cracking of bacon fat, and reaction of the unsaturated products with bromine.

Materials: Bacon, forceps, H-3, two culture tube stoppers, bromine.

Procedure: Tilt an unstoppered bottle of bromine to spill the vapor into two culture tubes; stopper at once. Project in H-3. Into tube one drop a strip of bacon, about 3 X '/% X in. Holding in the forceps, heat a similar strip of bacon in H-3, and when the bacon sputters and drips, drop it into the bromine in culture tube 2; stopper at once.

Observations: Tube 2 becomes colorless in a few sec- onds. Reason: Heating bacon fat cracks it into un- saturated acrolein (CH,=CH-CHO; this causes the acrid choking odor from burned bacon); the double bond of the unsaturated compound adds bromine, de- colorizing the tube.

Dem. 665-Preparaiian af Aceiylene

To show: Preparation and combustion of acetylene.

Materials: Fresh calcium carbide, cell H-1.

Procedure: Project cell H-1 with the generator con- taining 1 lump (5 mm3, no larger, CARE) of CaC2, and water in the medicine dropper and the receiver. Col- lect gas in the holder; test with a lighted match.

Observations: Acetylene, caught in the gas holder, explodes with air when a match is applied to it.

Reactions: CaC2 + 2HOH - Ca(0H)s + C%H, t ; 2C2Hz + 50% -+ 4C02 + 2H20.

Dem. 666-Acefylene Formed in a Ballaon

Experiment developed by Carl J. Maneuso.

To show: Balloon swelling as acetylene is generated in it.

Materials: Rubber balloon, lump of fresh CaCz, thread, medicine dropper, Bunsen burner.

Volume 46, Number 9 , September 1969 / A633