Organic Chemistry (Reactions) – Flashcards
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What free radical is most is likely to be formed from bromination?
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A tertiary radical (Most stable)
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What are nucleophiles?
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Electron-rich species that are attracted to a positively polarized atom (i.e. a carbonyl carbon)
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What is a better nucleophile I or F?
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Flourine
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What is a better leaving group I or F?
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Iodine
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What doesn't a nucleophile play a role in the rate of an Sn1 reaction?
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It is not involved in the rate-determining step...the formation of the carbocation.
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What factors will help carbocation formation and therefore increase the rate of an Sn1 reaction?
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1. Highly substituted carbons. 2. Polar solvents (Surround and isolate the carbocation) 3. Good leaving groups (Weak bases)
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Why is a Sn2 reaction bimolecular?
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Its rate-determining step is dependent on TWO species; both the substrate and the nucleophile.
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What are the best conditions for an Sn2 reaction?
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You must have a strong nucleophile for the backside attack (thats what she said) with no steric hindrance.
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With respect to optical activity, what do your end products of Sn1 and Sn2 reactions become?
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Sn1 = racemic mixture (nucleophile can attack from either the top or the bottom of the planar carbocation), therefore loss of optical activity. Sn2 = inversion of configuration and remains optically active.
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What role does tosylate usually play in reactions?
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It usually acts as a good leaving group and a good protecting group.
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Whats another word for ethyne?
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acetylene
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How do you make OH- a good leaving group for Sn1 and Sn2 reactions?
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For Sn1 you can protonate it and make water the leaving group. For Sn2 you can convert it to tosylate which is also a good leaving group.
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What is jones reagent and what does it do?
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it is CrO?, H?SO? in acetone and it oxidizes primary alcohols to carboxylic acids (STRONG!)
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Do ethers boil at high or low temperatures?
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Low...no H-bonding.
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How can you get ketones or aldehydes?
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Oxidation of primary or secondary alcohols. Or ozonolysis of alkenes.
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How do you get an acetal or ketal?
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When an aldehyde or ketone reacts with two equivalents of alcohol. A hemiketal or hemiacetal you get from one equivalent of alcohol.
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What is a cyanohydrin?
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When al and ke react with HCN.
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What is a wittig reaction and what is its goal?
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The goal is to make CARBON-CARBON double bonds by converting aldehydes and ketones into alkenes.
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What oxidizes an aldehyde and what do you get?
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KMnO?, CrO?, Ag?O, H?O? and you get a carboxylic acid.
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What reduces aldehydes and ketones?
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LAH or NaBH?
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What are the reagents for Wolff-Kishner Reduction of al and ke?
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H?NNH?, then a base and heat.
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What are the reagents for Clemmensen Reduction?
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Hg(Zn) and HCl
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Why are carboxylic acids that much more acidic?
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Resonance stabilization of between the alcoholic oxygen and the carbonyl oxygen.
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Electron withdrawing vs donating...what do each do to a negative charge and acidity?
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Withdrawing delocalize/stabillize the negative charge (spread it over the molecule) which increase acidity. Donating do the opposite.
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What is significant about the ? hydrogens on a ?-dicarboxylic acid?
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They are very acidic due to stabalization!
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Only primary alcohols can be oxidized to carboxylic acids. T/F?
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True!
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Is there a way to convert primary and secondary alkyl halides into carboxylic acids? Sure!!
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nitrile formation followed by acid or base catalyzed hydrolysis.
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How do you form an ester with a carboxylic acid?
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Addition of a primary alcohol under ACIDIC conditions.
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When might decarboxylation occur?
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When carboxylic acids are heated, they may spontaneously loose a CO?
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What is the order of reactivity for carboxylic acid derivatives?
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Acyl halide ; anhydrides ; esters ; amides
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How do you get an acyl halide from a carboxylic acid?
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SOCl?
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Friedel Crafts Acylation
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Aromatic ring acylated through electrophillic aromatic substitution.
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Reduction of acyl halide?
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H? Pd/BaSO? Quinoline
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How can one make an anhydride?
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React a carboxylic acid with a carboxylate salt or heat! to stabilize the carboxylic acid.
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The conversion of a carboxylic acid into ANYTHING depends on what?
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The nucleophile!!
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When carbonyl's are attacked by hydrolysis, what does the nucleophile look like in acidic vs basic conditions?
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Acidic: H?O is attacking Basic: OH- is attacking In acidic conditions the carbonyl oxygen is protonated.
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How can you think of Lithium Aluminum Hydride?
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It is like an H- nucleophile.
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Can nitrogen containing compounds form hydrogen bonds?
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Yes, but the are not as strong as the hydrogen bond between H and oxygen! (Therefore lower boiling point).
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Can nitrogen-containing compounds be optically active?
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Usually not because of nitrogen inversion but sometimes they can be isolated if the structure hinders inversion.
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How what is Gabriel Synthesis for?
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Gabriel drank ammonia! OH NO!
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What is hofmann rearrangement?
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An amide to a primary amine (Pg 389)
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What is a wash?
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When you are using the extraction to remove impurities rather than separate out the desired product.
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Gravity filtration vs vacuum filtration
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Gravity filtration is used for when the desired product is in solution (usually hot) where as vacuum filtration has the desired product being a solid.
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Why is temperature important in recrystallization?
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The product needs to be soluble in high temps and insoluble in lower temperatures. IMPURITIES need to be soluble at all temperatures so that they stay in solution.
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When would distillation be favored over a separatory funnel?
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When two liquids are miscible, the separatory funnel cannot be used therefore distillation is more ideal.
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When is vacuum filtration used?
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ABOVE 150 C BOILING POINTS! Vacuum will lower the pressure of the apparatus to ensure that the liquids do not decompensate under the extreme temperatures.
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Fractional distillation
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Repeated distillations on inert objects like glass beads that help separate two liquids with boiling points less than 25 C apart.
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Thin-Layer Chromatography
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Silica gel is polar!!
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Column Chromatography
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Ion Exchange Chromatography Size-Exclusion Chromatography Affinity Chromatography
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In gas chromatography what is the eluant and what is the stationary phase?
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The eluant or mobile phase is a gas (He or N) and the stationary phase is the temperature-regulated column. Retention time: How long it took for each compound to travel through the column.
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How does isoelectric focusing work?
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All proteins have an isoelectric point (no charge). When the molecule reaches the field that is equal to its isoelectric point, it will stop moving!
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How do Agrose gel and SDS-PAGE electrophoresis separate molecules?
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Based on SIZE
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What is the purpose of Infrared (IR) spectroscopy?
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Certain bonds absorb infrared light at different frequencies and this can then be measured through what is absorbed vs what is transmitted. Used for FUNCTIONAL GROUP identification.
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The difference between oligo and polysaccharide?
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Oligo is short poly is long.
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Where do you start numbering a carbohydrate?
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On the carbonyl end.
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What are epimers?
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Diastereomers that differ in the configuration of ONE carbon.
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What are anomers?
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They differ only in the newly formed chiral carbon (after ring formation). Can be ? vs ?. Glucose the ? anomer is trans and the ? anomer is cis (both pointing up!)
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Monosaccharide ester formation
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All hydroxyl groups will be esterified!
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What happens in a Tollens' Test?
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Testing for the presence of a reducing sugar. Aldoses and ketose can be oxidized to carboxylic acids and therefore reduce Ag+ in the Tollens' test to metallic silver (Ag+ to Ag)
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What happens in a Benedict's test?
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Testing for the presence of a reducing sugar. Aldoses and ketose can be oxidized to carboxylic acids and therefore producing Cu?O (red) from benedict's reagent (started with Cu(OH)?
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How do you get glycosides from your hemiacetal monosaccharide?
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Alcohol in the presence of ACID!!
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How do you get a disaccharide?
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From the same reaction that gave us the glycoside! Its just that now the alcohol is.....ANOTHER MONOSACCHARIDE! YAY!
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What kind of bond does Cellulose have vs Starch and glycogen?
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BETA 1, 4 vs the ALPHA of starch and glycogen (some ? 1,6 in there too!)
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What is the only amino acid that is NOT CHIRAL?
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Glycine
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Naturally-occuring amino acids are L-enantiomers. T/F? Fischer projection?
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True!! Fischer projections of amino acids have amino group to the left!
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What is a zwitterion and how does an amino acid look as such?
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They are dipolar ions where each half neutralizes the other.
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Amino acids are amphoteric. Why?
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They can act as an acid or a base. They have at least two dissociation constants (from H's on the n and c terminus)
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When does an amino acid take on the zwitterion form?
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At the isoelectric point or isoelectric pH between pKa? and pKa?
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What looses an H first in basic titration, the amino or carboxyl group?
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The carboxyl group duh!
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Things to know about titration of amino acids...
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1.Buffering capacity is greatest at the Ka's 2. Two moles of base need to be added in order to deprotonate one mole of most a.a. 3. When adding base, the carboxyl group looses the H first. 4. Titrations can be done in reverse starting with a basic solution and adding acid.
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How many moles of acid are needed to neutralize 1 mole of a basic amino acid?
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3 moles because of the extra R amino group.
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What is an amino acid called after it becomes a part of a peptide?
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A residue.
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Why is rotation of the peptide bond limited?
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There is resonance about the C-N bond giving it some double bond character.
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What level of structure is guided by hydrogen bonds for proteins?
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Secondary structure resulting in ?-helix and ?-pleated sheets.
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What level of structure determines whether you have collagen or myoglobin?
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Tertiary structure in that at this level you have the determination of fibrous vs globular proteins.
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What is a conjugated protein?
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One that gets part of their function from a prosthetic group.
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What is zaitsev's rule?
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When producing alkenes (usually from elimination reactions) there will be a major and minor product, the major one being the more subsituted and stable form.
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What is a Diels-Alder Reaction?
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