• Hot Ice:  Synthesis and Characterization of Sodium Acetate Trihydrate

    Hot Ice Crystallization

     

    Note:  This video assumes 80% acetic acid AKA "vinegar concentrate", not the usual 5-6% strength.  It is much more hazardous and gives off unpleasant fumes.  I do not currently have any 80% vinegar in stock.  I currently have a gallon of 30% acetic acid on order, so plan for that!  
      
    Part I:  Synthesis of Sodium Acetate Trihydrate (NaCH3COO.3H2O)

    Reaction 1:  Na2CO3 + 2 CH3COOH + 2 H2O → 2 NaCH3COO.3H2O + CO2
    Reaction 2:  NaHCO3 + CH3COOH + 2 H2O → NaCH3COO.3H2O + CO2
    Reaction 3:  NaOH + CH3COOH + 3 H2O → NaCH3COO.3H2O + H2O

    You can synthesize sodium acetate trihydrate by any of the 3 reactions above.  Watch the video above, and read the "Chalk Dust Magazine" article below, and decide which reaction you wish to pursue.  You should consider safety and reagant availability as factors, and be able to justify your choice.

    Write a procedure for synthesis of sodium acetate trihydrate based on the references given here and any other sources you have found.  Be sure to cite your sources!

    Hopefully you will see a nice crystallization of sodium acetate trihydrate along the way.  Does the 'ice' heat up or cool down in the process?  Take note of any observations.

    Note:  Despite the video, I do not allow you to handle chemicals with your bare hands in the laboratory.  That can just end badly in so many ways.

    Part II:  Heat Storage of Sodium Acetate Trihydrate (NaCH3COO.3H2O)

    Weigh out a known amount of sodium acetate trihydrate.  If your synthesized supplies are insufficient, I may be able to provide you with some more.  Melt it and allow it to cool to a supercooled liquid.  Be sure to use a very clean container and avoid any dust or debris, which may cause your supercooled liquid to crystallize prematurely.

    Use a thermometer to measure the temperature of the liquid before and after it crystallizes.  You may add a small 'seed crystal' of solid to start the crystallization if necessary.

    Calculate the heat energy given off:  the change in temperature, ΔT, multiplied by the specific heat capacity (C) will give you the energy given off by crystallization in units of J/mol.  You can multiply this value by the molar mass (in g/mol) to obtain the energy in J/gram.

    Compare this with values from the "Chalk Dust Magazine" article and the Wikipedia entry.  Is it comparable?

    Compare this with the energy density of lithium batteries.  Is this a good means of energy storage?

    Part III:  Demonstration

    Can you come up with an eye-catching demonstration of the crystallization of sodium acetate trihydrate? 

     

    References:

    http://chalkdustmagazine.com/blog/creating-hot-ice/

    https://en.wikipedia.org/wiki/Sodium_acetate

    How to Make Hot Ice at Home (Video Link)

    Bananas and Orchids:  Ester Synthesis Project

    Ester functional group Mechanism of acid-catalyzed esterification

    Esters are a class of organic compound which often have distinct odors (and flavors, but we don't eat anything we make!)  You may have already synthesized an ester, ethyl salicylate, from aspirin, but if not, it's okay.  Esters are generally formed from a carboxylic acid (R-COOH) and an alcohol (R'-OH).  This reaction is a double displacement where the -OH of the acid and the -H of the alcohol become water, H2O.  Organic chemists refer to this type of reaction as a 'condensation'.  This reaction will not happen without a catalyst.  Either acid or base catalyst may be used, but we generally use sulfuric acid (H2SO4).  Sulfuric acid is a good catalyst for esterifications because it tends to soak up the water product and drive the reaction forward.

    Safety note:  Concentrated sulfuric acid is extremely hazardous, a single drop can produce a burn with a lifelong scar and can permanently blind an eye instantly.  You will never handle it: I will either mix it with your reaction myself, or provide you a premade mixture of sulfuric acid.  The mixture is still hazardous, but not as much as concentrated sulfuric acid.  Gloves, goggles, and an apron are a must!

    Part I:  Synthesis of isopentyl acetate (Commercially sold as "Banana Oil")

     Isoamyl acetate synthesis

    Reaction:  C5H12O + C2H4O2 → C7H14O2 + H2O

     

    I am attaching a reference for the preparation of isopentyl acetate (AKA isoamyl acetate).  Unfortunately, we do not have the exact equipment specified - we do have all the ingredients, and we have the 'reflux' and 'distillation' equipment, but we do not have the 'electric flask heater' as of yet.  I am considering using a hot water bath and using a longer reaction period, as described in my 'Esterification of Salicylic Acid' procedure from last year.  I am also considering the use of a 'sand bath' heating method which allows higher temperatures than a water bath.  We may also consider trying a small 'microscale' pilot run first where we don't purify by distillation, but see if we're on the right track!

    Once you've got a workable procedure, we can try it!

    Part II:  Synthesis of isopentyl salicylate (Supposedly smells like orchids?)

    Reaction:  You can figure it out!  Instead of acetic acid (C2H4O2), you'll be using salicylic acid.  We may have already made salicylic acid from aspirin.  If not, look it up!

    Isopentyl salicylate is not as common a compound as isopentyl acetate.  However, it is used in perfumes.  Some sources claim it smells like orchids.  Please adapt the procedure again to prepare isopentyl salicylate.

    We may have already demonstrated that ethyl salicylate, when mixed with sugar and ground in a glass mortar in the darkroom, gives off light.  Try the same experiment with isopentyl salicylate.  Does it work?  How well? 

    References:

    Synthesis of Isopentyl Acetate (Department of Chemistry, Chulalongkorn University, www.chemistry.sc.chula.ac.th/bsac/Org%20Chem%20Lab_2012/Exp.8[1].pdf)

    Wiki entry on isopentanol (AKA isopentyl alcohol, AKA isoamyl alcohol)

    Wiki entry on acetic acid (AKA ethanoic acid but nobody calls it that)

    Wiki entry on salicylic acid

    Esterification of Salicylic Acid (Lab Handout from Last Year)

     

    Manganese Violet Pigment Project

    Manganese Violet Pigment

    Manganese violet is a pigment we use every year for the 'Make Your Own Paint' activity.  However, we do not always get consistent color - the product is often darker in color than it should be.  I hope that we can optimize the process to get better Manganese Violet.

    Part I:  Preparation of Monoammonium Phosphate

    Monoammoniumphosphate Crystal Monoammonium Phosphate Powder


    Reaction 1: H3PO4 + NH3 → NH4H2PO4 (monoammonium phosphate, the desired product)

    Reaction 2: H3PO4 + 2 NH3 → (NH4)2HPO4 (diammonium phosphate, an undesired product)

    We have household ammonia, approximately 3 Molar NH3 in water.  We also have 85% phosphoric acid, H3PO4.  Note that this is a concentrated acid and a hazard. 

     Your challenge here is to perform reaction 1 to prepare the desired product, monoammonium phosphate (), without having reaction 2 generating the undesired byproduct diammonium phosphate ().  As you see, reaction 1 has 1 moles of NH3 reacting with 1 mole of H3PO4 , while reaction 2 has 2 moles of NH3 reacting with 1 mole of H3PO4 . How do you get the correct product? 
    HINT:  You either add ammonia to phosphoric acid until the mixture turns basic by pH paper, or you add phosphoric acid to ammonia until the mixture turns acidic.  Which way is best?

    Once you've done the reaction, you should have a solution of monoammonium phosphate.  You will need to crystallize it and collect the solid monoammonium phosphate for the next step.

    Part II: Preparation of Manganese Violet

    Reaction:  NH4H2PO4 + MnO2 + H3PO4  → NH4MnP2O7 + ?????? (this reaction is not completely understood)

     As described in the reference below, monoammonium phosphate (NH4H2PO4 ), manganese dioxide (MnO2 ), and phosphoric acid (H3PO4 ) are heated in a ceramic dish together.  Once the reaction is complete, the mixture is boiled in water to remove soluble impurities, collected on a filter, and dried. 

    Here's the tricky part:  the 'preparation of manganese violet' paper below probably has the wrong amount of manganese dioxide.  They suggest using 10 grams (0.115 mol) of MnO2 with 10.6 grams (0.092 moles) of NH4H2PO4 - this is bad, because the product ends up having leftover MnO2 in it.  MnO2  is a very strong black pigment, and entirely ruins the purple we're trying to make.  I suggest, for your first try, you use half as much MnO2 as the paper suggests. 

    You will need to scale the recipe according to how much monoammonium phosphate you have available.  Maybe only use half of it for now?

    Part III: Optimization of Reaction Conditions

    Try the reaction a second time, using some other amount of MnO2 - perhaps one quarter?  Ideally, you can run both reactions at once, in separate ceramic dishes on the same hotplate.  Be sure you know which one is which!

    Compare the two products.  Which one looks like better Manganese Violet?

    After you have done this, propose some other mixtures to try.  Remember we are keeping the original proportions of monoammonium phosphate and phosphoric acid, we are only changing the amount of MnO2.

    References:

    Wiki entry for Monoammonium Phosphate

    Preparation of Manganese Violet

     

     
    Cinnamaldehyde Clock Project
     
     
    Cinnamaldehyde Clock Reaction
     
    Part I:  Time Trials
     
    Cinnamaldehyde and Acetone react to give Product  
    For detailed reaction mechanism, please see the entry for 'Raspberry Ketone Project'
     
    Reaction:  2 C9H8O + C3H6O → C21H18O + 2 H2O
     
    Note:  Organic chemists call this reaction a 'condensation'.  This is their term for a double displacement which yields water as a product.
     
    Safety Note:  This reaction requires the use of NaOH or KOH base.  These are strong bases and can cause severe burns!   
     
    Do reaction using stock solution of cinnamaldehyde, alcohol, and KOH with different amounts of acetone added.  Plot out time for different amounts of acetone and empirically fit a 'rate law': a mathematical expression which predicts reaction time.
     
    Once you have calculated a rate law, try to set up a series of test tubes which turn at 15 seconds, 30 seconds, 45 seconds, 60 seconds, and so on.  A chemical clock!  Practice and perform this demonstration for the class.
     
    Collect solid reaction product (1,9 diphenyl 1,3,6,8 nonatetraene 5-one AKA "Dicinnamalacetone") on filters for later testing.
     
    Part II:  Test dicinnamalacetone product as paint pigment
     
    This product is not thought to be very toxic, and happens to have a bright yellow color.  This makes it an attractive candidate for use in the annual Paint Pigment Project. You may need to grind it in a mortar to get it to mix well with latex paint medium.  Please take careful notes of masses or volumes of dicinnamalacetone and paint medium used, as well as any added water if necessary for 'thinning'. Mixed paint should be brushed on test papers and tested for stability of color.  At least one sample should be left in direct sunlight for an extended period of time. 
     
    By itself dicinnamalacetone has potential to give a brighter yellow that we currently have available with iron 'ochre' pigments.  It is possible that mixing it with some degree of red iron oxide and manganese violet could give brighter red tones as well.  It would also be interesting to test the final paint mix for fluorescence under a 'black light'.
     
    Part III:  (Advanced Cross-Project) 
     
    If a group is doing the 'raspberry ketone' project, they will be 'hydrogenating' double bonds in aldehydes.  Coordinate with them to do this reaction on some cinnamaldehyde in order to obtain dihydrocinnamaldehyde.  Do this on a small scale (< 0.1 gram), as this compound is reputed to have an extremely strong odor highly distinct from the original odor of cinnamaldehyde. 
     
    Hydrogenation of Cinnamaldehyde
    Reaction:  C9H8O + NH4HCO2 → C9H10O + NH3 + CO2
     
    References:
    Raspberry Ketone Project
     
    Part I:  "Aldol Condensation" of 4-hydroxybenzaldehyde with acetone
     
    Base-catalyzed reaction of acetone with 4-hydroxybenzaldehyde  
     
    Reaction:  C7H6O2 + C3H6O → C9H10O2 + H2O. 
    A "condensation" is what organic chemists call a double displacement where one product is water.
     
    Safety Note:  This reaction requires the use of NaOH or KOH base.  These are strong bases and can cause severe burns!   
     
    Part II:  Hydrogenation of 4-hydroxybenzalideneacetone to raspberry ketone (AKA "Frambinone" or "Rheosmine")
     Aldol condensation followed by 'transfer' hydrogenation
     
    Note:  I would write it NH4HCO2, with the ammonium cation first, 'ammonium formate'.  Why is it useful?  It's basically solid hydrogen storage: it gives off NH3, CO2, and H2.  The H2 adds across the double bond under the influence of the Pd catalyst to give a single bond.
     
    Reaction:  C9H10O2 + NH4HCO2 → C9H12O2 + NH3 + CO2
     
    Safety Note:  This reaction is performed in methanol as a solvent.  Methanol is toxic and flammable.  Furthermore, the palladium-carbon catalyst is quite capable of igniting methanol vapors.  For this reason the catalyst must be added to the reaction before the methanol.  I will dispense the methanol into your reaction for you, and we will conduct this reaction on a very small scale so that if it does ignite, it will not endanger anyone.
     
     
    References:
     
    Iron Oxalate Project
     
    Part I:  Preparation of FeC2O4.2H2O (Iron (II) Oxalate Dihydrate)  and "Pyrophoric Iron"
     
    Reaction 1:  Fe+2 + H2C2O4  → FeC2O4 + 2 H+
     
    Reaction 2: FeC2O4 → Fe + 2 CO2
     
    Reaction 2 is conducted by heating a small amount (<0.5 g ) of  FeC2O4 in a test tube. The product is iron, but a very special form of iron : it has a very high surface area due to being composed of fused nanoparticles, and therefore it is so chemically reactive that it will ignite upon contact with air.  
     
     
    Yellow iron (II) oxalate
    		 Pyrophoric iron burning when exposed to air
     
    Part II:  Preparation of Na3Fe(C2O4)3 and K3Fe(C2O4)3 (Sodium and Potassium Ferrioxalate)
     
    Reaction:  3 K2C2O4 + 2 FeC2O4 + H2C2O4 + H2O2 → 2 K3Fe(C2O4)3 + 2 H2O
     
    Reaction:  3 Na2C2O4 + 2 FeC2O4 + H2C2O4 + H2O2 → 2 Na3Fe(C2O4)3 + 2 H2O 
     
    Note:    Na2C2O4 and K2C2O4 will probably have to be prepared by reaction of H2C2O4 with NaOH or KOH respectively.
     
    Both Na3Fe(C2O4)3 and K3Fe(C2O4)3 are light sensitive:  upon exposure to light, they decompose.  Research this reaction and devise a demonstration of it. 
     
    Part III:  Growth of 'mixed salt' crystals of K5Na(Fe(C2O4)3)2 
     
    Reaction:  5 K3(Fe(C2O4)3).3H2O  + Na3(Fe(C2O4)3).3H2O → 3 K5Na(Fe(C2O4)3)2
     
    Grow crystals from a saturated solution of both potassium and sodium ferrioxalate salts.  Note that these salts decompose in the presence of light, and the crystallization may take days or weeks, so a safe location for the experiment must be found.
    "Mixed salt" Sodium Potassium Ferrioxalate Crystal  
     
    References:
     

    Student-Suggested Project:  Reduction of Pepto-Bismol to Bismuth Metal
    Bismuth subsalicylate hydrolyzed to chloride and displaced by aluminum metal
     
     References: