CHEM6BL Final Gainer
acid base properties of methyl orange
At pH> 4.4: - methyl orange exists mostly as the yellow negative sulfonate ion At pH< 3.2: - the dipolar red ion (helianthin) predominates
Why can methyl orange stain nylon and wool strongly?
Because the dye can bind to ionic or polar functional groups present in the fabric. Being highly charged and polar means more interactions and stronger bonds. The weaker ones are long nonpolar hydrocarbon chains.
isotopes of Br in mass spec
Bromine has two isotopes, 79Br and 81Br in an approximately 1:1 ratio (50.5 : 49.5 if you want to be fussy!). That means that a compound containing 1 bromine atom will have two peaks in the molecular ion region, depending on which bromine isotope the molecular ion contains.
fragmentation of alkyl halides in mass spec
C- Br breaks heterolytically C-Cl: a base peak of 42 means heterolytic break. can also be broken homolytically
isotopes of Cl in mass spec
Chlorine has two isotopes, 35Cl and 37Cl, in the approximate ratio of 3 atoms of 35Cl to 1 atom of 37Cl.
how many signals will the H-NMR of ferrocene have?
HNMR of ferrocene has a single signal b/c all H attached to cyclopentadienyl anion are equiv; if Fe(II) cation were attached to single carbon, there would be two signals
In the oxidation of benzoin to benzil. The benzil product is tested to see if there is non-oxidized benzoin present by adding NaOH. If it turns purple, then that means benzoin is present. What is the product formed and why does it have intense coloring?
The structure of this purple product is a benzoin enolate that has a conjugated aromatic group and carbonyl groups. This causes resonant delocalization and allows the enolate to shift into the visible light spectrum.
why is this reaction done at room temp
The reason why the reaction is performed at room temperature is because the energy does not need to be released through heat; heat is released through the emitted light
why must the polymerization step have a basic solution? - if not basic, will your yield be affected and how?
The solution must be basic because the hexamethyldiamine must be in its basic form in order to react with adipoyl chloride. - if not basic it will lower our yield
why are the phenol groups on the same side sterically?
We need Br to be anti to H. In order for this to happen, we need extra energy. having the Ph groups on the same side produces steric hinderence that gives the high energy we need.
Horner-Wadsworth-Emmons Reaction
a modifaction of the Wittig reaction, this reaction involves reacting aldehydes or ketones with stabilized phosphorus ylides (phosphonate carbanions), leading to the production of olefins with excellent E-selectivity.
how does the imine get selectively reduced?
hydrogens are added across the double bond
fragmentation of ethers and amines in mass spec
fragmentation pattern similar to that of alkyl halides. can break homolytically or heterolytically
advantage to using a phosphonate ester
gives a cis- vs trans- isomer. metalated phosphonates are used to get the trans product of stilbene.
condensing
heating pdt mixture to evaporate off any excess solvent leaving pure product
this reaction requires (high/low) heat. what was used to get the reaction to the temperature needed
high, pyrex tube and bunsen burner
why is it necessary to wait until the imine is fully formed before adding NaBH4?
if it was added before the imine was fullt formed, the NaBH4 could react with the intermediate ion and the product would not be pure
reductive amination
imine formation and reduction. a two step procedure that allows for the synthesis of complex amines from relatively simple starting materials
how does diazonium ion react with dimethylaniline?
immeditaley.
what impurities are removed when the product is washed with 5% NaHCO3 in fischer esterification?
impurities are removed by 5%. removed carboxylic acid (remainng acid from catalyst)
tetrophenylcyclopentadienone is an _________. how does it form the benzene ring to create hexaphenylbenzene?
intermediate. electrong push to carbonyl group, and the electrons push back to form a new double bond, creating a six membered ring (benzene).
what is the electrophile and nucleophile in aldol condensation
nuc: alpha carbon of ketone elec: carbonyl carbon of aldehyde
aldehyde used? primary amine used?
o vanilllin, p toluidine
what is the purpose of the boiling stone in fischer esterification and other reactions?
prevent substance from superheating and it creates a more controlled boil
purpose of drying tube in Fischer esterification (and other reactions)
prevents water from enetering the reaction
why does this reaction have to be vigorously stirred?
to ensure that the two phases met. If the reaction was left unstirred, the reaction would not happen because the reagents would not come in contact. By using a phase transfer catalyst and stirring, this ensured that the reagents would meet and therefore react.
imination
when an aldehyde or ketone is treated with a primary or secondary amine
what is the solvent in the Fischer esterification? what is the limiting reagent?
alcohol nucleophile, alcohol (n-propanol)
pKa of aldehyde, propene, and propane and how they relate
alde: 20 ene: 43 ane: 60 propene has lower pKa bc it is sp2 hybridized vs sp3 hybridized. aldehyde is weakest conj base so it has lowest pKa
purpose of triethylene glycol
allows reaction to mix homogeneously. Also has high bp and can withstand the high energy needed to make this reaction happen- hexane or ether could not do that
what is the co-oxidant in this reaction? what is it used for?
ammonium nitrate, used to regenerate the Cu2+ species
McLafferty rearrangement
an example of a hydrogen atom jumping to the other fragment as a part of the process of the bond breaking. It happens in an organic molecule containing a keto-group.
if a secondary amine is used in imination, what is the product called and what can it do?
an iminium ion- can quickly tautomerize to an enamine
toluene
common non polar solvent
diethylether
common nonpolar solvent
DMF
common polar solvent
acetate
common polar solvent
ethanol
common polar solvent
ethyl acetate
common polar solvent
water
common polar solvent
acetone
common solvent used to clean glassware- polar
DMSO
common solvent, dissolves polar and non polar compounds
column chromatography: what is it and how is it done?
common technique used to separate individual compounds from a mixture. You can use column chromatography on both a small or large scale to isolate and purify material for use on a later experiment. it is done by first selecting a column, selecting a stationary phase and filling the column (silica gel is what we used), selecting the eluent used, loading the column, running the colun, analyzing the eluted fractions, and isolating the different components. the more polar the analyte, the more polar the eluent should be.
bis aldol condensation
condensation reaction in organic chemistry in which an enol or an enolate ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone
is this multistep synthesis convergent or linear?
convergent
convergent vs linear synthesis
convergent: happens in a sequential order, one step at a time. To get percent yield of total synthesis, you simply multiply each individual yield together. linear: running two or more reactions at the same time to get the desired product. you can find toal yield by multiplying the individual yields for the longesr linear sequence.
what is the catalyst in this reaction?
copper (II) acetate
MeoH _______ the solubility of _______
decreases, tetrophenylcyclopentadienone
what is NaOH used for
deprotonate phosphate
polarity of ferrocene, acetylferrocene and diacetylferrocene
diacetylferrocene is most polar. ferrocene is least polar so it will elute first. diacetylferrocene will elute last
DCM
dichloromethane. common nonpolar solvent
how to find Rf
distance travelled by spot / distance travelled by solvent front
purpose of Hickman still in Fischer ester.
distillation to purify the product.
IR, HNMR, CNMR, mass spec
do practice problems online. be comfortable interpreting and predicting structures. For mass spec, know that m/z peak is molecular formula
the short version of the synthesis of 1,4-dihydropyridine was used in this lab. why is this method so advantageous?
does not require a lot of solvent
mechanism of diphenylacetate from stilbene
double bond of stilbene attacks bromine of pyridinium tribromide. this forms a triangle thingy on the Br, and the Ph groups are anti. Br ion attacks the carbon and breaks the triangle, so we now have one Br on both sides. But we want Br and H anti! So bond rotates to make them anti and Ph on same side. Once this is done, our elimination process is done. OH- of our strong band attacks a hydrogen, forming a double bond and breaking off one of the Bromines. This elimination repeats on the other side, forming diphenylacetylene
which groups is responsible to the increased chemiluminescence of vanillin?
electron withdrawing group- tend to stabilize electronic charge
redox reaction
electrons are lost feom one atom or molecule and gained by another. oxidation= loss, reduction = gain of electrons.
azo coupling mechanism explanation
electrophilic substitution. new group is introduced into the molecule (electrophile). attaches to molecule, and water removes extra hydrogen
Chemiluminescence
emission of light as a result of a chemical reaction. reverse of photochemical reaction. When a chemiluminescent material glows, the molecules become excited and produce a photon. This excited state is caused by an electron being promoted to a higher electron shell level, which creates an increase in energy level since the electron has moved to a higher energy level. When the electron falls back to its original electron shell- its ground state- this is when the photon of light is emitted, and the molecule produces a color
what steps were taken to ensure fischer esterification went to completion?
excess reagent (carboxylic acid in this case) was used Le Chatelier's principle: adding more reactants shifts the reaction to the right towards the products
principles involved in TLC: mobile phase, solid (stationary) phase, solvent polarity
mobile phase: The mobile phase flows through the stationary phase and carries the components of the mixture with it. solid (stationary) phase: The solid or liquid phase of a chromatography system on which the materials to be separated are selectively adsorbed. solvent polarity: Non-polar compounds move up the plate most rapidly (higher Rf value), whereas polar substances travel up the TLC plate slowly or not at all (lower Rf value). The eluting strength of a solvent is primarily related to how strongly it adsorbs onto the adsorbent. Because typical adsorbents are highly polar, eluting strength increases with solvent polarity. low polarity compounds are elute with non polar solvents, and poalr compounds are eluted wigh highly polar sovlents
Mass spec: M+ peak
molecular ion peak. The peak on the mass spec that correlates with the molecular weight of the compound. teh heaviest ion
is 1,4-dihydropyridine a pharmacophore? a privileged structure?
no, yes
Why protons at alpha position to a carbonyl group more acidic?
- Because the enolate form is super stable, so the alpha carbon is more likely to lose its proton to gain this enolate form. More likely to lose proton→ acidic AF. - The more effective the resonance stabilisation of the negative charge, the more stable the conjugate base is and therefore the more acidic the parent system.
what was the function of hydrogen peroxide and sodium bisulfate in experiment 10B?
- Hydrogen peroxide was used as the co-oxidant. the reduced tungsten compound is transferred back to the aqueous phase in which it will rect with hydrogen peroxide to convert it back to oxidized tungstate. (therefore need an excess amount of H2O2). * hydrogen peroxide will re-oxidize tungstate and this allows it to be ready to oxidize another molecule of cyclohexene - Sodium bisulfate provides the counter ion for the tungstate
fragmentation of alcohols in mass spec
-alcohol M+ ions fragment so readily that few survive to reach collector - MS of primary & secondary alcohols show weak M+ peaks. break homolytically - peak at 18 shows loss of water
why does addition of NaBH4 make the color of the solution turn white?
-broke down conjugation by reducing the double bond
fragmentation of carbonyl carbons in mass spec
-unlike alcohols, have strong molecular ion peak - undergo homolytic α cleavage; largest α substituent most readily cleaved
Experiment 13B: Reductive Amination
...
Experiment 14B: Phenyl Grignard Addition of benzophenone
...
Experiment 15B: Synthesis of the 1,4- dihydropyridine privileged structure
...
Experiment 16B: Chemiluminescence
...
Experiment 16C: Synthesis and Purification of Acetylferrocene
...
Experiment 17B: Multistep synthesis part 1: HWE addition of benzaldehyde
...
Experiment 18B: Multistep synth p 2: synthesis of diphenylacetylene from stilbene
...
Experiment 19B: Multistep synthesis part 3, oxidation of benzoin to benzil
...
Experiment 20B: Synthesis of Hexaphenylbenzene
...
Experiment 9B: Fischer Esterification
...
Experiment 10B: Multistep Synthesis of Nylon- 6,6 from cyclohexane
....
Experiment 11B: Aldol Condensation
....
Experiment 12B: Synthesis of a dye, Methyl Orange
....
steps of reaction: cyclohexane to nylon
1: oxidation of cyclohexene to adipic acid using sodium tungstate 2. adipic acid to adipoyl chloride by using a catalytic amount of DMF
what can be learned from TLC?
1) determines number of cmpds in mixture 2) establishes whether two compounds are identical 3) follows course of reaction
filtration: vacuum and pasteur filter pippettes
1) vacuum filtration - used to rapidly and completely separate a solid from the liquid with which it is mixed 2) pasteur filter pipets - minimal loss of org liquid; used for small amt of org liquid/solution that can be separated from solid rxn by-pdt or drying agent
mechanism for part 4
1. dibenzil acetone reacts with OH group to form an enolate 2. enolate reacts with benzil, creating a carbonyl group and attaching benzil to the carbon next to Ph group 3. water reacts with negatively charged oxygen to form OH group. 4. OH group reacts with hydrogen, deprotonating the C=O bond 5. O- collapses on self, plucking off OH group 6. Oh group deprotonates C=O again 7. O- collapses again and forms the ring 8. O- reacts with water to form OH 9. OH deprotonates C=O 10. O- collapses again and plucks off OH 11. reacts with diphenylacetylene to make product
mechanism
1. electron transfer fro Cu2+ to O of carbonyl. 2. AcO- species attacks H od carbon attached to OH, forms double bond in between 3. this double bond is unstable, so the double bond gets switched to the C=O position. one electron from O collapses, one electron from double bond goes towards double bond and other electron gets put on carbon attached to OH 4. this electron gets transferred to the Cu2+ species, leaving a positive charge on that carbon. AcO- comes in again and removes H from OH group, forming a C=O bond. this creates benzine.
Why does Sulfanilic acid has to be first dissolved in Na2CO3 solution before forming diazonium salt? Why does Nitrous acid has to be formed in situ before forming diazonium salt? Why does the reaction mixture have to be keep below 5 C?
1. sulfanilic not soluble in acids, so an alkaline (Na2CO3) solution is made then HCl is added, precipitating reactive sulfanilic out while forming nitrous acid from sodium nitrite→ diazonium salt is insoluble in HCl so it will precipitate out & reacts with the N,N-dimethylaniline to form methyl orange (this step is the azo coupling step) 2. The precursor sodium nitrite is in the alkaline solution (with the sulfanilic acid) and then HCl is added to the solution, forming the nitrous acid. 3. Diazonium ion is very unstable and will form N2 gas
what is the phase transfer catalyst in this reaction? where does phase transfer catalysis occur in the HWE reaction?
Aliquat 336. interface of the two liquids.
hexanes
A common solvent. Nonpolar.
anhydrous conditions
A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water, therefore, it is important that water-free reagents and techniques are used.
in oxidation of benzoin to benzil, qhat accepts an electron and from where? what gets a hydrogen removed and what removes it?
Cu+ acceptd electron from oxygen while the acetate ion removes a hydrogen.
directing groups
Directing groups promote substitution at certain positions. Ortho, para directing groups are electron-donating groups; meta directing groups are electron-withdrawing groups.
Mass spec: heterolytic vs homolytic bond cleavage
Homolytic cleavage produces free radicals — atoms with unpaired valence electrons. In heterolytic cleavage, one atom gets both of the shared electrons.
why is the ether solvent necessary?
Mg is electron deficient and the ether solvent is able to use its lone pair electrons to coordinate to the Mg and donate electron density to it
oxalate chloride and phenol reaction
OH attacks Cl and Cl gets kicked off, Cl ion deprotonates OH. This process repeats for Cl on other side
_____ are an important class of compounds in organic chemistry. What is this synonymous with? What is the most mild an convenient way to synthesize this?
Olefins. Alkene. Horner- Wadsworth-Emmons reaction
Recrystallization what is it and how is it done?
Process of dissolving crude crystals in a solvent to remove impurities. Impurities remain in solvent and crystals reform in a purified form. it is done by dissolving the impure solid at a high temp, filtering the solution if there is an insoluble fraction, cooling the solution slowy to control the recrystalllization process, filtering the crystals, then dting the crytals
structural tendencies of chemiluminescent molecules
Structurally, certain arrangements of molecules will produce different wavelengths of light. The complexity of the molecule can determine the color produced by the molecule; for example, conjugated, complex molecules produce color more often than simple molecules. This is because the ground and excited states of conjugated molecules are closer in energy, and less energy can be used to excite the electrons to produce a color .
how to prepare a TLC plate/TLC chamber
TLC plate: silica gel plate, draw one line 1 cm from bottom. dot reagent desired and whatever compound you want to compare it to. TLC chamber: choose a solvent, grab a beaker and place solvent in beaker. place filter paper in the beaker so solvent can move up place TLC plate in and put watch glass over the beaker
Mass spec: base peak
The most intense (tallest) peak in a mass spectrum, due to the ion with the greatest relative abundance
What is Fischer esterification?
The procedure involves a reaction of a carboxylic acid with an alcohol using an acid catalyst
Why electrophilic aromatic substitution occurs at para position in this reaction?
When there is an electron donating group it is a ortho/para director, with para being favored due to steric hindrance on ortho, because due to resonance the ortho/para are negatively charged (and were doing an electrophilic substitution) and meta positively charged.
Why do we have to make sure that the yellow residue in this reaction is removed before doing recrystallization?
Will make it so that no crystals form - The PTC was very greasy and when a crystal lattice is trying to form grease interferes with this and prevent s any crystals from forming
pKa relationship of phenols and the chemiluminescence that was observed
With pKa, it has been found phenols have an enhancement effect as their pKa values increase.
basic summary of the reaction happening
a beta keto ester (either Me or Et as the R group) reacts with an ammonium and an aldehyde at 80 degrees C for 10 minutes. this creates the dihydropyridine.
classical Hanztsch synthesis is performed in either ______ or _______
acetic acid or alcohol as solvent; usually has low yields or long reaction times
what is the polar solvent
acetic acid, which boils at a high temp (120 C)
Ferrocene is highly _______, so acetylation occurs readily using a mild ____ ______
activated, acid catalyst
polymerization mechanism explanation
active species adds to one side of double bond, creating active carbon. active carbon adds in same manner to new monomer molecule. backbone grows through repeated addition of active end to new monomer
Activating vs deactivating substituents
active: increase rate of reaction, donate electron density deactuve: slow rate of reaction, accept electron density
Friedel-Crafts Acylation
addition of a benzene ring at carbonyl carboxylic acid derivative
grignard reaction mech explained
addition of organomagnesium halide to a ketone or aldehyde to form a secondary or tertiary alcohol. MgBr gets attached to a carbon, forming a double bond and deprotonating carbonyl. this then reacts with water to give the alcohol
Why do we not purify the adipoyl chloride prior to using it in step 3?
adipoyl cannot be isolated b/c it is difficult to extract because it reacts violently with water so the crude from is better
explanation of the phase transfer process
aqueous sodium hyroxide is needed to generate the carbanion intermediate, but is not miscible (its in the aqueous layer) with the hexane solvent used to dissolve the phosphonate and benzaldehyde, so it cannot react to deprotonate the phosphate. This is where the phase transfer catalyst comes in. Aliquat 336 accelerates the process by exchanging its chloride ion with a hydroxide. This molecule can then enter the hexane layer (organic layer) where it deprotonates the phosphonate. eventually the ammonium ion becomes a counter ion for diethylphosphate, and this species can shuttle back to the aqueous layer where phosphate is exchanged for hydroxide to repeat the process
why is the trans isomer of stilbene the solid vs the cis isomer?
because of the forces acting on stilbene. Trans- stilbene is mainly composed of planar phenyl rings that have effective pi bonds that help strengthen the molecule. The cis- isomer is not at planar due to steric hindrance, and therefore has weaker pi bonds.
diacettylferrocene remained at the top of the column during chromatography while acetylferrocene and ferrocene traveled faster. why? how could we elute it?
because of their polarities; since ferrocene is the least polar it travels the farthest and since diacetylferrocene is the most polar it travels the least. Since ferrocene is less polar, is traveled very far by just using the non-polar solvent of hexane. 1:1 ether: hexane was used as the more polar solvent to elute the more polar acetylferrocene- this is why the solvent were changed while eluting. We would have to use a very polar solvent to get diacetylferrocene to move
why can acidic hydrogens not be used and why must we run the experiment under anhydrous conditions?
because the grignard reagent readily reacts with carbonyl compounds to form new C-C bonds, and because it is such a strong base, acidic hydrogens and water will quench the grignard reagent. Water, alcohols, carboxylic acids, carbon dioxide, esters are some examples or groups that will kill grignard reagent
in first step, what reagent gets deprotonated? which does the deprotonation? why is this?
benzil. dibenzil acetone. this is because dibenzil acetone has 2 alpha carbons with 2 alpha hydrogens that can only deprotonate, and beznil has no alpha hydrogens
what is the on polar byproduct you get rid of in the petroleum ether washing step?
biphenyl; if phenyl bromide is not fully used up, grignard reagent can react with it to form biphenyl
what reactions occur to produce hexaphenylbenzene
bis-aldol condensation followed by a Diels-Alder [4+2] cycloaddition with diphenylacetylene
reflux
boiling a solution while continually condensing the vapor by cooling it and returning the liquid to the rxn flask if heated in open sys: solvent and other liquids would evaporate if heated in closed sys: pressure would build and explode
Aldol Addition
c-c bond forming reaction. converts an aldehyde to an alcohol
acidic form of methyl orange absorbs more light. why
it has a bigger conjugation system due to being protonated. The protonation brings a positive charge on the nitrogen pulling electrons more and thus causing more conjugation. (large wavelength low energy higher intensity)
why is copper acetate used?
it is a great oxidizer and is less toxic
why is product created not a good Ca2+ blocker?
its not a privileged structure, therefore is does not have the necessary functional groups to make it be a recognizable ligand by biological enzymes
Aldol Condensation Mechanism explanation
ketone such as acetone can be deprotonated with hydroxide to form an enolate - the enolate can attack the carbonyl c of an aldehyde like benzaldehyde forming new c-c bond and a beta-hydroxxy ketone - newly formed alc can undergo elim rxn which forms alpha-beta unsaturated ketone and water
what is electrophile/nucleophile in redutive amination
ketone/ aldehyde is electrophile and primary amine is the nucleophile.
extraction: what is it and how to do it
liquid-liquid extraction involves the distribution of a solute in two immiscible solvents. DCM is more dense than water so org phase is bottom; otherwise org is top layer. on a small scale, it is done by placing solution into a vial and then adding the organic solvent. a stopper should be placed on it and the vial should be shaked to ensure the two phases interact. the bottom layer (aqeuous) is to be removed and trasnfered, and the organic layers left are to be combined, dried, and solvent should evaporated.
why do you need vigorous stirring in this reaction?
make sure tungstate and cyclohexene come in contact
3 step mech
mech: step 1 attack of the beta ketoester anolate on the aldehyde, and an E1cB elimination takes place to get the unsaturated carbonyl compound. E1cB elimination involves the O ion attacking the hydrogen next to it, creating a double bond and causing the carbonyl oxygen to deprotonate. the O ion from the carbonyl then relapses on itself, the double bond rearranges and the OH group attacks the ammonium, leaving the molecule and forming water. mech: step 2 formation of an ester enamine. produced by the condensation of the second equivalent of the beta ketoester with ammonia. condensation is an organic addition. this means that the NH3 reacts with the C=O bond, adding NH2 onto the moleule and creating an OH group. OH group gets kicked off, creating water, and a double bond is made mech: step 3 michael addition between two fragments, followed by proton transfers and an intramolecular enamine formation. michael addition is the nucleophilic addition of a carbanion to an a,b- unsaturated carbonyl compound.
phase transfer catalyst
occurs at the interface of two liquids. when two reagents that need to react with each other are immiscible (are in two different phases) a phase transfer catalyst can be used to bring the necessary functional group to the necessary reagent in the other phase. Aliquat 336 is an example of this
azo coupling
occurs btw a diazonium salt (ion) and an activated aromatic substrate
Hantzsch 1,4-dihydropyridine synthesis
one pot cyclocondensation reaction occurs between an aldehyde, ammonia, and 2 equivalents of a beta ketoester. this creates ,4-dihydropyridine that can be oxidized to form the corresponding pyridine derivative.
mechanism for fischer esterification explanation
pg 56 in lab book. alcohol gets protonated by protic solvent. this oxunium ion is active catalyst species that protonates carboxylic acid. This protonation causes carboxylic acid to attack alcohol, which forms an unstavle tetrahedral intermediate that undergoes proton transfer. after water gets removed, we get a protonated ester that is then deprotonated by the solvent
Acid chloride formation mechanism explanation
pg 66 of lab book. adipic acid is made through oxidation. a catalytic amount of DMF solvent is used to react with oxalyl chloride to produce an active Vilsmeier chlorinating agent. this species allows the conversion of CA to acid chloride
methanol
polar solvent
what is the electrophile in the azo coupling mech
pos charged diazonium ion
privileged structure vs pharmacophore
privileged structure: it contains structures within itself which have the capabilities of being recognized as a ligand by biological receptors. acts on a certain target to get a biological reaction Pharmacophore: a part of a molecular structure that is responsible for a particular biological or pharmacological interaction that it undergoes. abstract conept
why is alcohol of a beta-hydroxy ketone easier to eliminate than a normal alcohol?
product is stabilized by resonance creating a double bond - due to conjugation its dble bond is more stable than a regular dble bond
how many stereochemical products can be produced if benzoin is a racemic mixture? if it is enantiomerically pure?
racemic: 4 enan: 2
Diels-Alder Cycloaddition
reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene derivative
drying
remove water from an organic liquid using a drying agent (usually anhydrous inorg salt) that reacts with water to form crystalline hydrates which are insoluble in org phase and can be removed by filtration
why do we use pyridinium perbromide instead of Br2?
safer and can be controlled better than Br2
what is used as the reducing agent in this reaction
sodium borohydride
reductuve amination 3 step mech explained
step 1 mechanism: imine formation 1. nucleophilic attack (lone pair on N attach carbonyl carbon and deprotonates the O) 2. proton transfer (depronated O reacts with base to become OH, base removes extra hydrogen from NH2 group to make NH) 3. protonation of OH (reaction with hydrogen of base to protonate to H2O) 4. removal of water (H2O gets removed) 5. deprotonation (N deprotonated by base) step 2 mechanism: imine reduction as soon as imine is formed, is attacked by the reducing agent (sodium borohydride) which generates the amine step 3 mechanism: acetylation of amine to form amide 1. nucleophilic attack by amine (amine attacks carbonyl carbon and O loses double bond) 2. deprotonation by the amine (amine deprotonates NH2 group) 3. leaving group is removed (carbonyl group)
how is nylon made?
step growth polymerization- polymers assembled form monomers that have reactive functional groups at each end of the polymer unit.
why does the reaction stay in the orientation it is in, despite the fact it can rotat freely?
steric hinderance prevents the Ph groups from being near each other
this reaction involves the synthesis of ____ from _____
stilbene from benzaldehyde
starting material is ____. we perform a ______ of the starting material, using ________ ______ as the source of bromine. this reaction occurs through an _____ ____ ____.
stilbene, dibromination. pyridinium tribromide. electrophilic addition reaction.
SAR study
structure activity relationship study. generating a large library of compounds and testing each of them against the enzyme or protein of interest. In this experiment, a small scale SAR study was done to investigate chemiluinescence; the results will be used to predict what other compounds could exhibit strong luminescence.
what is the acid catalyst in the fischer esterification?
sulfuric acid (H2SO4)
percent yield: formula and how to use it
take actual yield from lab. take theoretical yield from limiting reagent and convert to g of product
diazotation
the formation of the diazonium ion intermediate which is formed by rxn of an aromatic amine with nitrous acid
purification
the physical separation of a chemical substance of interest from foreign or contaminating substances. Pure results of a successful purification process are termed isolate. methods include extraction, crystallization/recrystallization, evaporation, distillation, etc.
distillation: what it is and how is it done? (simple and fractional)
the process of vaporizing a liquid, condensing the vapor, and collecting the condensate in another container. great for separating a liquid mixture when components have two different melting points. simple: used when compound is already almost pure. vapor rises in the distillation flask and comes into contact with a thermometer. the vapor passes through a condenser which re-liquifies the vapor and guides it into the receiving flask. fractional: used when two compounds have similar boiling points. same as simple but a fractionating column is used; this allows collection of different fractions by the rotation of this receiver. with each cycle in the column, the composition of the vapor is progressively enriched in the lower boiling component. the more cycles, the more pure our separation will be.
limiting reagent
the reactant that determines how much of the products are made. The other reactants are sometimes referred to as being in excess, since there will be some leftover after the limiting reagent is completely used up.
melting point
the temperature (energy=heat) at which crystal lattice breaks (solid to liquid) determines identity and purity of product lower, broader = impure packing increases melting point range. intermolecular forces determine melting point range as well (hydrogen>dipole-dipole>London or Van der Waals)
limiting reagent in this reaction is
triton B
what is the main oxidant and reactant of this reaction? how do these two interact with each other?
tungstate, cyclohexene, phast transfer catalyst
washing
two immiscible liquids are separated, the organic layer is extracted (washed) with water or a dilute aq solution of an acid or a base. Salts formed are soluble in water but not in typical organic solvents so they are easily transported into the aqueous phase
why is NaH2CO added to the filtrate?
used as a neutralizing agent.
why did you not stir the polymerization reaction?
you will get a mush of nylon when you want the monomers to build up on each other slowly from the interface to form the polyamide