Q1 What is a drying agent? Why do we need them? What do they do? How they do so depends on the drying agent, but they remove water molecules from an organic solvent.
Back to the Chem b main page Q: Will the Final exam emphasize the chapters or will it also be more of a comprehensive final?
It will be comprehensive. My intent is that all the chapters will be equally represented on the final. There are overlapping themes in many of the chapters, i. Themes somtimes reappear in subsequent chapters with expanded scope or emphasis amine synthesis and amino acid synthesis.
So the themes may be represented more so than the individual chapters. Will you be offering the alternate final exam on Wednesday, May, 3rd? As stated on the syllabus, there will be no alternative final exam offered. Just to clarify, we do not need to know the amino chart in the beginning of chapter 26, right?
You do not need to know the structures amino acids per se by popular demandbut you should be able to identify a hydrophobic, hydrophilic, basic and acidic amino acid when you see one. I was also unsure as to whether or not specific structure knowledge for portions of chapter 27 i.
As with Competing nucleophiles 2 butanol amino acids, you do not need to know specific structures, but you should be able to identify specific classes of compounds. On slide we have a heading for section Are we to assume the material from slide really do fall under the same caption as Chapter 28 Q: I believe they actually made 3'-CTAG-5'.
They synthesized the the DNA backwards. Be sure to remember that the chemical synthesis of DNA and peptides is done in the opposite deirection as the convention for writing a sequence. Why is chemical DNA synthesis done 3' to 5'? The primary 5'-hydroxy group is less hindered and therefore more nucleophilic than the secondary 3'-hydroxy group.
For the same reasons as above. The DMT group is pretty big and reacts much faster with less hindered primary alcohols 5'-OH than more hindered secondary alcohols and not at all with tertiary alcohols Q: How can diisopropylamide act as a leaving group when it is the conjugate base of an extraordinarily weak acid?
The pKa of tetrazole is about 4.
Tetrazole is an activator in this reaction and protonates the nitrogen of the phosphoramidite. This makes the diisopropyl ammonium a much better leaving group.
Chapter 26 Q: Why do we use acetamidomalonate with the amide group rather than aminomalonate with an amine?
The amide is ultimately hydrolyzed to the amine, but why begin with the amide? A free amino group is nucleophilic and would compete in the SN2 reaction with alkyl halides. Why use the cyclic acetal protecting group during enantioselective catalytic hydrogenation slide ? It simultaneously protects both hydroxyl groups as acetal of formaldehyde.
Protecting 1,2-diols as acetals or ketals is standard. Could you provide the mechanisms for the penultimate and ultimate steps of the derivatization with ninhydrin slide ? The penultimate step is the hydrolysis of an imine.
So it would be the reverse mechanism as the formation of an imine Chapter The ultimate step is the formation of an imine with a second equivalent of nunhydrin. What is the purpose of amino acid analysis determining the percent composition of each amino acid if peptide sequencing via Edman method provides this information in addition to the linear amino acid sequence?
Sequencing is done on small fragments. The amino acid analysis is can be done on the entire protein. Since these are large macromolecules, determining structure is much more challenging and the error associated with each method is larger.
Amino acid analysis is another piece of data that serves as a check for other methods.or ketone is not complete, with several theories competing to explain the data. For numerous hydride reductions of 3-X butanones (X=F, Cl, Br), the selectivity for the major syn isomer is signiﬁcantly and consistently higher for X=Br than for.
Experiment Nucleophilic Substitution Reactions: Competing Nucleophiles. Experiment 21A: Competitive Nucleophiles with 1-Butanol or 2-Butanol. Experiment 21B: Competitive Nucleophiles with 2-Methylpropanol. Experiment 21C: Analysis. Experiment Hydrolysis of Some Alkyl Chlorides. EXPERIMENT # 5 NUCLEOPHILIC SUBSTITUTION REACTIONS (SN1 and SN2) Prelab Answers 1.
Which is a better nucleophile in aqueous solution, Br– or Cl–?Why? Bromide is the better nucleophile in aqueous solution. Jul 01, · The key word is tend to be - if there's a competing acid-base reaction that can happen, it almost always will.
2) size. CN- for instance is a very small nucleophile and all else being equal will have smaller steric interactions (key phrase - all else being equal - it never is). CHM Nucleophilic Substitution Lab to a stronger base, the nucleophile. Nucleophilic substitution reactions may occur by one of two common mechanisms, designated S N 1 and S N 2.
S N 2 Mechanism: The S N ( mL) of 1-butanol, and 10 mL of 48% HBr into a mL round bottom flask. Cool the mixture in the ice bath. Chapter 10 Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds PROBLEM 3 Explain the difference in reactivity between CH 3OH 2 and CH 3OH in a nucleophilic substitution reaction.
(The pK a of H 3O + is ) PROBLEM 4 SOLvEd Show how 1-butanol can be converted into the following compound.