AIRFREE TECHNIQUE AND SENSITIVE REAGENTS S ECTI O N 1: GLASS W ARE A ND E Q UIP M ENT. A. Using a manifold

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1 AIRFREE TECHNIQUE AND SENSITIVE REAGENTS S ECTI O N 1: GLASS W ARE A ND E Q UIP M ENT Some organic compounds are air sensitive. They can react with the water vapor or oxygen in the air. In order to perform an air-sensitive reaction, we must employ airfree technique and work under an inert atmosphere. A. Using a manifold A glass manifold (also called a Schlenk line) is a piece of glassware that enables us to perform an airfree reaction. The manifold is comprised of two hollow glass tubes; the front tube contains ports. Each port has a valve or three-way stopcock, which allows one to switch between inert gas and vacuum. Our manifold is connected to a tank of nitrogen, an inert gas, and a vacuum pump that resides below the hood. We use two types of vacuum lines in the FRI lab. The thick-walled tubing should only be used for pulling vacuum, and the thinner plastic lines are best used to run reactions, as they are pliable and easily moved around. If the line comes in contact with any organic compound (your compound, solvent) it should be changed immediately, as this can contaminate a subsequent reaction. Fact: The plasticizer from the tubing we use contains an aromatic ester. If solvent goes up the line and comes back into a flask (i.e. in a distillation) the plasticizer begins to dissolve in the solvent and may make an appearance in your NMR! 1. Make sure the manifold is connected to the nitrogen tank and that the tank is on. Check the flow using the bubbler at the end of the manifold. 2. Adjust the flow of nitrogen through the manifold. 3. If vacuum is required, put dry ice and acetone into the vacuum trap (acetone needs to be refilled about twice a week). In this step, you re making a bath to cool and condense the solvent so that it doesn t get into the pump. You need not fill the trap all the way up with acetone. 4. If the glass knob is horizontal, the system is closed. Turn the knob so that N 2 is flowing or vacuum is pulling. 5. Important lab etiquette: Be certain to turn your valve to neutral before you remove your reaction from the manifold. Failure to do so could ruin someone else s reaction. 6. When you are done: Make sure no one needs the manifold or vacuum. Turn off all three valves on the N 2 tank (to the right righty tighty.) Open one of the lines so that the vacuum is sucking (the vacuum will get loud and gurgle), and then turn vacuum pump off using the switch on the front of the pump. NEVER HEAT A CLOSED SYSTEM.

2 B. Drying glassware In order to run an air-sensitive reaction, all glassware must be thoroughly dried in an oven or flame-dried. The basic technique is described below: Oven Drying 1. Dry the piece of glassware in the oven for 2 h (or overnight). Note: If the item contains any Teflon parts, remove them and put them in the dessicator. 2. Using tongs and the heat glove next to the oven, quickly transfer the item to the dessicator and allow it to cool. Flame Drying 1. Put a stir bar into the flask. 2A. Flame-drying under vacuum: Clamp your flask to the monkey bars. Fit the flask with a vacuum adapter, and evacuate the flask using the manifold. 2B. Flame-drying under nitrogen: Fit the flask with a septum and clamp to the monkey bars. Put two 18 G (pink) needles in the septum, and introduce a stream of nitrogen into the flask using a cut off 1-mL syringe attached to the manifold. 3. Put a stir bar into the flask. 4. Using the blowtorch, thoroughly flame-dry the flask beginning at the bottom and ending near the nitrogen inlet or glass adapter. If using a septum, be sure not to scorch it! 5. Hot glass looks just like cold glass. Do not touch the flask until it has cooled for ample time (~10 minutes). C. Purging glassware Once the flask is dried, any air that is in the flask must be removed and replaced with nitrogen (or argon) gas. This can be accomplished using a technique called purging, in which the air is evacuated from the flask under vacuum, followed by backfilling, in which the inert gas is introduced into the flask. If a reactant is a solid, the flask may be purged with the solid inside of it. Alternatively, the solid can be dissolved in a suitable solvent, and the resulting solution can be transferred into the air-free flask via a needle through a rubber septum. Method 1: Using vacuum 1. If appropriate, put a stir bar and non-volatile reagents into the flask, according to your procedure. 2. Attach a cut off 1-mL syringe to the manifold via the rubber tubing. Put an appropriately sized needle on the 1-mL syringe and introduce it into the flask through a rubber septum.

3 3. Evacuate the flask then backfill with nitrogen three times. Because you re only pulling vacuum briefly, you may use the thinner tubing. 4. Introduce your solvent into the flask through the septum. 5. Follow your procedure: Liquids will be introduced through the septum either neat or as solutions, and solids will be introduced as solutions. Method 2: Using nitrogen gas 1. Fit the flame-dried piece of glassware with a septum (don t forget the stir bar). 2. Insert two needles into the septum. 3. Attach a cut off 1-mL syringe to the manifold via the rubber tubing. Make sure nitrogen gas is flowing through it and connect it to one of the needles in the septum. 4. Allow a stream of nitrogen to purge the flask for several minutes. You may choose to turn the nitrogen up at this point if it won t disturb anyone else s reaction, but turn it down once you re done purging. 5. When you re done: Remove the vent needle and adjust the nitrogen gas flow, if appropriate. Method 3: Via balloon 1. Fit the flame-dried piece of glassware with a septum (don t forget the stir bar), and put one needle through the septum. 2. Affix a balloon to a 3-mL syringe using a rubber band. 3. Using the nitrogen tank directly, purge the balloon by filling slightly then allowing the balloon to deflate. Repeat three times. 4. Put a needle on the end of the balloon and put the needle through the septum. Allow the flask to purge for several minutes (watch your balloon you may need to refill). 5. Remove the vent needle used for purging, and then quickly refill the balloon to the desired size. Put the needle from the balloon back through the septum. Purging needles 1. Open a new needle and syringes and affix the needle to the syringe. 2. Put the needle into a flask that contains an atmosphere of inert gas (preferably your reaction flask). 3. Draw back a little bit of the inert gas from the flask. 4. Remove the needle from the flask and expel the gas from the needle. 5. Repeat steps 2 4 two more times. S ECTI ON 2: R EAGEN TS There are many reagents in organic chemistry that require special handling. Some reagents or compounds can be air or light sensitive, and may require very specialized handling. In general, follow these rules for handing reagents, and always talk to your RE, as TA, or mentor before using a sensitive reagent that you haven t used before.

4 Opening a new reagent Write Open and today s date on the bottle using a Sharpie. Air or moisture sensitive reagents that contain a sure seal: A sure seal prevents a compound from exposure to air or moisture. Located below the cap, the sure seal allows you to remove a reagent with no exposure to air, if you have good technique. 1. Open the sure seal bottle. 2. Using a 22 G needle (BLACK ONLY!) introduce a balloon of inert gas or a stream of inert gas from the manifold. Be certain that there is not too much pressure from the gas line. 3. Affix a second black needle to a syringe, and purge this needle three times using your reaction flask, ideally. You must never purge using the sure seal bottle. It will cause the seal to give out and ruin the reagent. 4. Remove the desired amount of reagent through the sure seal using the syringe. NEVER PUT AN AIR SENSITIVE REAGENT BACK INTO THE REAGENT BOTTLE. If you put too much into the syringe, you must take it. Reagents can be very expensive; please don t ruin them on us! 5. Once the reagent is measured (try to get rid of air bubbles as much as possible without putting reagent back into the flask), draw a small amount of nitrogen into the tip of the needle. This will prevent quenching of the reagent upon transfer. 6. As quickly and safely as possible, transfer the needle from the reagent bottle into the septum of your purged reaction flask. 7. Remove the needle delivering inert gas to the reagent bottle. Cap the bottle and parafilm as quickly as possible. Reagents without a sure seal that are not aqueous solutions 1. Open the bottle and syringe out the desired amount of reagent. 2. Using a balloon and in the hood, blow a stream of nitrogen into the bottle and quickly cap the bottle using your other hand. 3. Parafilm the cap. 4. Store as indicated on the bottle. Your compounds 1. Using a balloon and in the hood, blow a stream of nitrogen into the vessel containing your compound. 2. Quickly cap the vessel using your other hand (use yellow Teflon caps for round bottom flasks). 3. Parafilm the flask. 4. Depending on how sensitive and/or precious the material is, store in the vented cabinet, refrigerator, or freezer.

5 S ECTI ON 3: T RAN SFE RRI NG AN D NEE DLES We mainly use six (6) different types of needles in this lab. Below is a list with the do s and don ts for each type: Short Needles 18 G, 1.5 needles (Pink, short) For purging large flasks or delivering large volumes from containers that do not have sure seals. Never pierce a sure seal with this needle. 20 G, 1.5 needles (Yellow, short) For purging smaller flasks or syringing reagents that do not have sure seals. 22 G, 1 needles (Black, short) Use to puncture sure seals and introduce nitrogen flow. Long Needles 18 G, 3 needles (Pink, long) Used for syringing large volumes. Never pierce a sure seal with this needle. 22 G, 3 needles (Black, long) For syringing reagents out of sure seal containers. Metal 12 needles 22 G, 12 needles (all metal) For syringing solvents from the solvent system or from large flasks through a septum. What s a cannula? (Pronounced: Can-you-lah) This is a needle that is sharp on both ends that is used to transfer liquids from one sealed container to another sealed container. This works by immersing the needle in the liquid you wish to transfer and also pressurizing that vessel. Using a cannula reduces the chance of exposing the liquid or solution to air. S ECTI O N 4: C LE ANING U P If you syringed up more reagent than you needed, you will have to quench that reagent. Depending on how sensitive the reagent is you may need to quench it under nitrogen. Ask your RE. In some cases, you may be able to suspend an addition funnel or separatory funnel above the reagent in an open vessel, and deliver a slow drip of the solvent that you are using to quench the reagent. Below is a procedure for quenching the still pot from a distillation in which the solution was distilled from calcium hydride (CaH 2 ): Quenching a still pot (CaH 2 ) 1. Cool the still pot in an ice bath and begin stirring with a magnetic stir bar.

6 2. Fill an addition funnel or separatory funnel with an appropriate amount of isopropyl alcohol (ask your RE or TA what an appropriate amount is for the scale you re on) 3. Using a waste beaker, adjust the funnel to deliver the isopropanol dropwise and slowly into the flask. 4. Once the solution is cooled, suspend the funnel over the flask using the monkey bars and allow the funnel to drip into the flask. If the solution begins to bubble vigorously, discontinue the drip until the solution calms down. 5. Once the isopropanol has been added, put a small amount of water in the separatory funnel. 6. Slowly drip the water into the flask. If the solution begins to bubble vigorously, discontinue the drip until the solution calms down. 7. Confirm with your RE or TA that the reagent is quenched. 8. Prepare a waste tag for the container you plan to pour your quenched reagent into. Fill it out in pencil. Put Kristen s name and approximate percentages of all components (your reagent, calcium hydride, water, isopropyl alcohol, etc.) 9. Secure the waste tag to the waste container using a rubber band. 10. Pour the contents of the still pot into the waste container, rinsing with water. Now that you have finished up, there may be a residue on your flask. Sometimes an acetone wash just isn t enough. There are several options available to thoroughly clean your glassware. 1A. (Optional) Base bath: This mixture of ethanol and potassium hydroxide cleans by removing a layer of the glass. 1B. (Optional) Acid bath (or rinse): Good for removing residual metals and other hard to clean residues from the flask. I generally use 3 N HCl. Nitric acid is also common for an acid bath. 2. Rinse the residual acid or base off with copious amounts of distilled water. 3. Clean the piece of glassware with acetone (rinse into the acetone waste). 4. Allow to dry, or dry with a stream of air. Note, when cleaning a separatory funnel, this process is slightly different: 1. Rinse any residual organic compound off by rinsing first with acetone into the acetone waste jar. 2. Rinse the separatory funnel with distilled water to remove any salts. 3. Perform a final acetone rinse and put on the rack to dry. This final rinse is essential, as it expedites the drying of the piece of glassware. As always, ask us if you re unsure!