Orgo lab exam 2
what are azo dyes? give examples
-account for 60-70% of dyes -structure is Ar-N=N-Ar' and the nature of the Ar controls the dye color, water-solubility of dyes, and how well they bind a certain fabric -the dyes are developed directly on the fabric. -exs: disperse orange 1 and para red
Why use ethanol in the saponification Rxn? Why do we reflux the Rxn? Why do we use saturated NaCl?
-ethanol is added to the reaction to facilitate the mixing of the fat (melted lard) and the aqueous sodium hydroxide solution while the reaction mixture is refluxed. Lard is not soluble in NaOH aq sol'n so ethanol speeds up the rxn by facilitating the dissolving of lard into the water to facilitate faster mixing. -we reflux bc saponification needs heat for the reaction, and none of the rxn is lost when refluxing -After refluxing, the reaction mixture is added to a saturated sodium chloride solution in order to precipitate the soap. The saturated sodium chloride solution increases the ionic strength of the aqueous layer and the soap will separate/ppt (will "coagulate"). The soap is then filtered and washed to obtain the final product.
classify polymers by reaction type. Differentiate the reaction types and give examples of each
addition and condensation polymers. -Addition polymers are obtained via addition polymerization when the monomers' double bonds are broken (e.g.: in the presence of a catalyst) and the molecules react to form a long chain polymeric molecule. Ex's: polyethylene, polyvinyl chloride (PVC), polystyrene. -Condensation polymers are obtained when bifunctional monomers react to form a long chain polymeric molecule; a small molecule (by-product) is eliminated during this reaction. Ex's: polyamides (Nylons), polyesters, polysaccharides (cellulose).
special cleaning in the dyes lab?
all glassware is to be rinsed w acetone then with hot water and detergent
Why do we reflux the reaction mixture in fischer? What is the approx. temperature of the reaction mixture during reflux?
allows the reagents to reach boiling with the vapors condensing back into the mix. We dont lose any of our reaction in this way. The bp is approx the bp of the solvent, which here is acetic acid bc the majority of the volume in the flask was acetic acid, and it has the lowest BP of the mix (aa, h2so4, isoamyl alcohol). 118oC.
what are the repeating units for: PVC, teflon, polyethylene, nylon 6.6, and nylon 6.10
PVC: [CH2-CHCl-] teflon: [CF2-CF2] polyethylene: [CH2-CH2] nylon 6.6: see notes nylon 6.10: see notes
define polymers. Synthetic vs natural polymers and ex's?
Polymers are large molecules (macromolecules) made up of many repeating units of smaller molecules (monomers). Natural polymers are like polysaccharides and proteins (silk, wool, DNA, cellulose). Synthetic polymers are human made, and examples are nylon, polyester, teflon.
what are all the ways that polymers ca be classified? which do we focus on?
Polymers can be classified as a function of: * Reaction type (addition, condensation)* Polymer growth (chain-growth, step-growth) Structure (linear, branched, cross-linked, etc.) Properties (thermoplastic, thermosets)
How did we purify the crude product in the DBA lab?
Recrystallize with hot ethanol (10mL per 4g crude added and heated until solid dissolves. then cooled to RT then on ice bath), then vacuume filtration and washed with 7mL 2X cold diethyl ether to wash crystals and then 6mL.
Why is benzaldehyde added before acetone? in the DBA lab
So that acetone reacts immediately with benzadlehyde and not with itself (which would form diacetone alcohol)
what determines the quality of a dyed fabric?
The quality of a dyed fabric depends not only on the dye, but also on the type of fabric and the process of dyeing. A good dye will not fade away when exposed to light, heat or washing.
temp requirements for dye lab?
must maintain rxn between 0-5oC because the diazonium salt is unstable above 5oC
special cleaning in fischer?
no
what is saponification? general saponification rxn? What is soap? How does soap clean?
-saponification is the hydrolysis of natural fatty acid esters (fats) under alkaline conditions; the products of the reaction are glycerol (aka glycerin, a trihydroxy alcohol) and soap(s) (salts of fatty acids). -see notes for general rxn -soap is salts of fatty acids -Based on the rule "like dissolves likes", soaps are able to clean because their polar head is attracted to water (hydrophilic), while their non-polar tail is water repelling (hydrophobic). The tail of the soap is attracted to the "dirt" and soap molecules will surround the dirt molecules forming soap micelles. The polar head, along with the dirt attached to the tail, can then be washed away by water
How can the relative quantities of the reactants determine the main product of the Rxn (monobenzalacetone vs. dibenzalacetone)?
Benzaldehyde in excess makes dibenzalacteone Acetone in excess will mainly form mono-benzalacetone
Product characterization: significance of MP range; % yield calculation, reasons for low yield; IR Spectrum (why is the C=O bond somewhat shifted?) (DBA lab)
MP range helps to show which isomer our product is. %yield is good to see how much we yielded compared to what was possible (reasons for low yield is lost product from dropping/spilling and maybe not stirring long enough for rxn to go to completion). C=O bond is shifted due to conjugation (shifts it down)
what is the role of NaOH and ethanol in the DBA lab? why is ethanol important
NaOH is the catalyst to deprotonate acetone and make enolate (CH2-) so it can attack the benzaldehyde. Ethanol is the solvent. The solvent used must easily dissolve the reactants (aldehyde and ketone) and intermediate (benzalacetone), but not the final product (DBA).
why was NaOH used in the nylon lab?
NaOH neutralizes the HCl that is released in the reation. if its not neutralized, the HCl will protonate the HMDA, so it does not have unpaired electrons. This means it can't act as a nucleophile and therefore will stop reacting with the SC.
summarize what we did in the nylon lab
Nylon 6,10 was synthesized from sebacoyl chloride (SC) and Hexane-1,6-diamine (hexamethylenediamine aka HMDA). The small molecule eliminated in this reaction is the hydrochloric acid, which is neutrallized with NaOH. Mixed sol'n A (SC + hexanes) and sol'n B (HMDA + NaOH) by pouring the lower density sol'n (A) over the higher density sol'n (B). Polymer formed, then was wound around the long noodle. the nylon and noodle were washed w water to get rid of excess naoh and then that strand was transferred to a short noodle and coils counted. Dried for a week then weighed that and scrap.
any special cleaning in the DBA lab?
aqueous filtrate from 1st filtration can be put in hood drain. 2nd filtration (organic) can be put in daily waste. Solid DBA to solid waste. rinse all glassware with acetone and then w hot soapy water then acetone (for a real good clean)
why was a small excess of ___ used in DBA lab
benzaldehyde aldehydes can become impure during storage due to their oxidation to carbacid. by using 2.2 equivalents of benzaldehyde we make sure that there is enough of it to fully react with all the acetone. (10% excess). also ensures formation of DBA rather than MBA
write the reaction for the synthesis of para red dye. what kind of dye is this. know LR/ theor yeild calcs. Any temperature requirements here?
developed, azo dye. see notes for rxn and calcs yes, rxn between 0-5oC bc the salt intermediate is unstable above 5oC
what type of dyeing method needs certain fabric and why? (2 fabric ex's)
direct dying: need fabric with many polar sites on their polypeptide chains, allowing to bind strongly to the polar groups on the direct dyes (wool and silk)
differentiate between direct (give 2 examples), mordant (give 1 ex), vat (give 1 ex), and developed dyes (1 ex and 1 fabric)
direct: are compounds that adhere to the fabric molecules without help from other chemicals. These are usually polar compounds and will combine well with fabric that has polar sites. Examples of direct dyes: Methyl Orange, Orange II. mordant: are dyes that are only capable to adhere to fabric through the use of a chemical intermediate, namely a mordant. Metallic hydroxides and tannic acid are often used as mordant substances. In this process, the mordant is applied to the fabric prior to the dye. On application, the dye will bond to the mordant. The final color is a result of both the dye used and the mordant. Often the same dye will produce different colors in combination with different mordant substances. An example of mordant dye is Malachite Green. vat: are insoluble in water and therefore incapable, in their colored form, of directly dyeing the fiber. They can be converted to a soluble form when reduced by another chemical. The reduced dye is applied to the fabric, and then exposed to the air which oxidizes the dye back to its colored form. Example of a vat dye is Indigo. developed: the dye-forming chemical reaction is carried out directly on the fabric. This process is frequently used to synthesize azo dyes (dyes containing a -N=N- structure in the molecule). The azo class accounts for 60 - 70% of all dyes. In today's lab we will use a process called ingrain dyeing to develop the Para Red dye. This process is widely used industrially to apply azo dyes on fabrics, especially on cotton.
Why are dyes colored?
dye molecules contain a chromophore group (conjugated part of the molecule) which can absorb certain wavelengths of visible light while reflecting complementary wavelengths
give me a rundown of what happened in the dyes lab.
first, the fabric was treated with base-treated 2napthol (2napthol+NaOH). Fabric placed in oven. 4-nitroaniline, NANO2, and HCl are combined to make the intermediate diazonium salt. This solution is dabbed onto the treated fabric and a red color appears.
what exactly did we do in the fischer experiment? summarize the steps
first, we synthesized isoamyl acetate from isoamyl alcohol and acetic acid using H2SO4 as a catalyst. 5mL isoamyl alc + 7mL glacial acetic acid + 10 drops h2so4 to an RB flask and reflux for 45 mins. Then transfer the RB flask to a cold water bath to cool to RT. Decant the liquid to a sep funnel. 20mL water, shake/vent, 10mL sodium bicarb, shake/vent, 10mL sodium bicarb, shake/vent, 10mL NaCl (The last step is a drying step with NaCl. This removes most of the remaining water from the organic phase), shake/vent. Dry w sodium sulfate. Final product smells like banana. Get IR spectrum. Second, we synthesize methyl salicylate from methyl alcohol and salicylic acid using h2so4 as catalyst. .5g salicylic acid + 5mL methyl alcohol + 10 drops h2so4, and heat. Smell the wintergreen
What method did we use to prepare Nylon 6,10 in the lab? Be able to explain the principle of this method. Why did we use sebacoyl chloride and not the carboxylic acid?
interfacial polymerization, which is a condensation polymerization technique, is where two reactive monomers, each dissolved in different solvents that are practically immiscible, react at the interface between the two solutions. The reaction is easier to run if a diacid chloride is used instead of the dicarboxylic acid bc acid chlorides are more reactive than their respective carboxylic acids, therefore the rate of the reaction increases.
soap made from walnut oil (5.3) and KOH will likely be: soap made from coconut oil (0.1) and NaOH will likely be:
liquid solid
summarize what you did in the saponification lab
made hard soap from lard and NaOH. 5g lard + 20mL water + 5g NaOH + 20mL ethanol was refluxed for 30 mins. This was cooled, then it was poured over ice cold saturated NaCl and chilled. The soap precipitated, and was filtered w vacuum filt and washed w wash solution (sat'd NaCl+water). pH was basic. It was then dried and compared to hand soap and lab detergent in terms of pH, cleaning power, foaming, and hard water. Our soap was most basic and hand soap least basic. Our soap was best cleaner. Our soap and handsoap were most foamy. Hard water removed foam in our soap and handsoap, but not in detergent. There was soap scum in ours but not the others.
what are the side products in the DBA rxn?
mainly monobenzalacetone
Isolating and purifying the isoamyl acetate product (work-up of the Rx mixture): what is accomplished in each step of the purification process?.. If reactions are taking place, know the chemical reactions.
purified in the sep funnel. First is Washing with distilled water (should wash off the unreacted isoamyl alcohol, H2SO4, and acetic acid). Then, Washing twice with Sodium bicarbonate which is an Acid - Base extraction; the remaining acetic acid and sulfuric acid in the flask will react with the sodium bicarbonate to be neutrallized: rxns in notes Then, washing with saturated Sodium chloride. This is done bc the NaCl will remove most of the remaining water from the organic phase Then, dried with sodium sulfate. Decant the liquid from the sodium sulfate w funnel
talk about the unsat/sat ratio. What does this indicate? What does a smaller and bigger number represent?
represents the percent by weight of sat'd vs unsat'd fatty acids present in different types of fats and oils. A larger value means more unsat'd which means more liquidy, and a smaller value means more sat'd which means more solid.
summarize what we did in the DBA lab.
rxn in notes. aldol condensation reaction between benzaldehyde and acetone using NaOH as catalyst and ethanol as the solvent. Carried out at 20oC to avoid reverse rxns. NaOH + water + ethanol was cooled to 20oC, then 6mL benzaldehyde was added, then 2mL acetone. More ethanol was then added. Stirring continues for 30 mins to ensure reaction completion. Cooled on ice bath and filtered w vacuum filt. Rinsed numerous times w water until pH of filtrate is neutral. Crude product is weighed to determine how much hot ethanol (10ml per 4g crude) is needed for recrystallization. Transfer crude and ethanol and heat until solid dissolves. Cool to RT then ice bath and do vacuum filt (rinse w 7ml cold diethyl ether 2X, then 6mL). Weigh and get MP and IR.
temp requirements for DBA lab?
rxn must be carried out close to 20oC bc aldol condensation is reversible at higher temps, so to drive the rxn right and ensure a high product yield, we carry out the rxn at 20.
in fischer est, give the alcohol and carbacid that produces: methyl salicylate, methyl anthranilate, methyl butyrate, isoamyl acetate, n-Octyl acetate, ethyl butyrate
salicylic acid + methyl alcohol = methyl salicylate Anthranilic Acid + Methyl Alcohol = methyl anthranilate Butyric Acid + Methyl Alcohol = Methyl Butyrate Acetic Acid + Isoamyl Alcohol = Isoamyl Acetate Acetic Acid + n-Octyl Alcohol = n-Octyl Acetate Butyric Acid + Ethyl Alcohol = ethyl butyrate know the rxns though!
saturated vs unsaturated fatty acids? soaps they make? list the ones we have to know
saturated: no double bonds (makes harder, less soluble soaps) unsaturated: double bonds (makes liquidy soaps) Saturated: capric (C10OOH), lauric (C12OOH), myristic (C14OOH), palmitic (C16OOH), stearic (C18OOH) unsaturated: oleic (C18^9), linoleic (C18^9,12), alpha linoleic (C18^9,12,15)
what is the general reaction for fischer esterifcation and the mechanism?
see notes
write the rxns for preparation of: nylon 6,6, Dacron (polyethylene glycol terephthalate), and nylon 6,10 (including preparation of sebacoyl chloride from thionyl chloride and sebacic acid)
see notes
what are the 2 rxns for preparing the esters we made in fischer? know the LR and theor yield calcs for fischer
see notes and lab report
what is the reaction for DBA formation via aldol condensation? what is the mechanism? how would you do the LR and theor yield calcs?
see notes and report for calcs
Dibenzalacetone isomerism; which isomer was mainly produced in our Rx; how do you know?
see notes for the isomers (trans trans, cis trans, cis cis). We made trans trans bc the mp was 110-111 which is what we got, and trans trans is crystalline solid which is what we got. the cis trans is solid but MP 60, and cis cis is liquid.
Be able to recognize the IR spectrum of an ester and identify the specific bonds
see notes. C-O (1230ish 1240ish) at ~1243 is only present in esters, so this verifies you have an ester. C-H (2900-3000) and C=O (~1735) are also present so seeing these could verify you have this product. C-O (1000-1200) at 1055 is present in esters and alcohols, so presence of this peak indicates either unreacted alcohol, verifies an ester, or both. If OH is present at ~3555, it can be due to leftover water from the NaCl extraction or incomplete drying by sodium sulfate. Or, unreacted alcohol left in the organic layer.
any special cleaning in saponificiation lab?
soap solutions go in drain. plastic weighing dish, plastic pipette, and all vials/caps are rinsed w tap water then 3x with DI.
Uses of Dibenzalacetone
sunscreen (it absorbs UV light)
NaOH vs KOH in soap making?
the alkali (NaOH or KOH) used in the reaction will also determine if a soap is liquid or solid at room temperature as well as the soap's solubility. For example, sodium hydroxide (NaOH) is used to make bar soap (a harder, less soluble soap) while potassium hydroxide (KOH) is used to make soaps that are liquid at room temperature.
how are polyamides named? (numbers following)
the number of carbons in the reagents. Nylon 6,10 is made from hexane 1,6-diamine (6C's) and sebacoyl chloride (10C's). Nylon 6,6 is made from hexamethylene diamine (6C's) and adipic acid (6 C's)
How can the yield be improved for the fischer Rxn? (shifting the equilibrium towards product formation)
through increasing the concentration of one of the reactants or by removing the byproducts of the rxn. When the acid and alc are in stoich quantitites, the yield is ~67%. when the reactant concentration increases 2x, the yield is ~85%. when it is increased 3x, the yield is ~90%. thus, all the options are: increase acetic acid conc, increase isoamyl alcohol conc, or decr amount of water
what species are still present in the RB after reflux in the fischer lab?
unreacted Isoamyl alcohol, isoamyl acetate, water, excess acetic acid, sulfuric acid (catalyst)
what is the reaction and process for dyeing denim?
vat dyeing, using the dye Indigo. the water-insoluble indigo is converted to a water-soluble form by reducing indigo with a chemical (commonly sodium hyposulfite). the reduced dye is applied to the fabric, and is then exposed to air which oxidizes the dye back into its colored form. see notes for rxn
What is "soap scum"? Chemical Rxn between soap and Ca2+ or Mg2+ ions.
when the Na+ ion in the soap is replaced with Ca2+ or Mg2+ in the water, you create a water- insoluble substance called soap scum. See notes for rxns. *check report*