orgo 2 Flashcards
1
Q
What is the IR absorbance for carbonyl?
A
1700cm^-1
sharp deep
2
Q
What is the IR absorbance for alcohol ?
A
3300cm^-1
broad separate from CH
3
Q
What is the IR absorbance for saturated alkane CH?
A
2800 cm^-1
sharp deep
4
Q
What is the IR absorbance of carboxylic acid OH?
A
3000 cm^-1
broad overlap CH
5
Q
What is the IR absorbance for amine NH?
A
3300cm^-1
broad shallow
6
Q
What is the IR absorbance for amide NH
A
3300cm^-1
broad deep
7
Q
what is the IR absorbance for nitriles, C=N ?
A
2250 cm^-1
sharp deep
8
Q
What does IR absorbance represent?
A
only represent a single polar bond within a molecule.
If there’s no dipole = no absorbance
9
Q
Who does UV light spectroscopy work?
A
When a molecule is exposed to UV radiation, electrons within that molecule will often absorb that energy and excite to the next highest energy level. ABSORBANCE is recorded on UV spectrum.
10
Q
Which molecules show no or low UV absorbance?
A
molecules that contain ONLY single bonds.
11
Q
Which bonds absorb molecules strongly?
A
double and triple bonds
12
Q
What molecules absorb even more UV than do isolated double or triple bonds?
A
conjugated systems.
The greater the degree of conjugation, the farther to the right the species will absorb.
13
Q
What is mass spectroscopy ?
A
the molecules of the sample are bombarded with electrons causing them to both break apart into smaller pieces and ionize, so you get fragments with different masses and charges. Only particles with a certain mass to charge ration (m/z) will follow the exact curved path necessary to NOT hit he walls and exit onto the detector at the end of the flight tube.
14
Q
On a mass spectroscopy, what does the parent peak represent? what does the base peak represent?
A
parent peak: represents the original molecule minus one electron (aka molecule ion peak)
base peak: most common fragment and is usually the most stable fragment generated = highest fragment generated
15
Q
Q5. If the velocity of particles in the flight tube of a mass spectrometer is held constant while the strength of the magnetic field is increased linearly, how will the mass of particles striking the detector vary with time?
A
A linear increase in the magnetic field will create a linear increase in the force exerted on the particles according to: F = qvBsin. For a curved flight tube with a detector at the far end, in order for any particle to strike the detector it must experience exactly the right centripetal acceleration to trace the precise curvature that results in striking the detector. As the centripetal force increases this will occur for increasingly massive particles. The graph below shows the linear relationship between magnitude of the B field and mass of particles at the detector.
16
Q
What is NMR?
A
Differentiate molecules based on hydrogen
17
Q
What must an atom have in order to register on an NMR?
A
odd atomic number or odd mass number.
18
Q
How does the MCAT think of MRI’s?
A
HNMR for the human body
19
Q
Nuclear spin causes small changes in the electric field and—as you should remember from physics—a changing electric field creates a ____?
A
magnetic field
20
Q
How do IR help us identify molecule?
A
based on function groups
21
Q
What do the peaks represent in a H-NMR?
A
peaks represent all the hydrogens in a molecule that share an indistinguishable chemical environment.
22
Q
What does the area under the H-NMR peak represent?
A
the number of hydrogens accounted for by the peak
23
Q
What is the absorbance range? what does it represent?
A
0 -12 ppm.
12ppm= downfield= deshielded
0 ppm= upfield = shielded
24
Q
What is the absorbance range of a C13-NMR spectrum?
A
0 -220ppm
220 ppm: downfield= desuhielded
0 ppm= upfield = shielded
25
What is the C13 NMR absorbance for C-C ?
0-50
26
What is the C13 NMR absorbance for C-O ?
50-100
27
What is the C13 NMR absorbance for C=C ?
100- 150
28
What is the C13 NMR absorbance for C=O ?
150- 200
29
1) The synthesis of the drug Prostratin from naturally occurring Phorbol is shown. The product is a mixture of Prostratin and unreacted Phorbol. Spectroscopic analysis is used to determine percent yield. An H-NMR spectrum for Prostratin would differ from an H-NMR spectrum for Phorbol in that the H- NMR for Prostratin would include:
A) one additional proton signal
B) two additional proton signals
C) one additional proton signal, one additional ester signal and two fewer alcohol signals
D) one less proton signal
D
30
what is the purpose of extraction?
to separate wo compounds based on solubility (polar and non polar layer)
31
In an extraction, is the polar solvent in the bottom or top layer?
non polar layer is less dense and often on top; polar layer is most often on bottom.
32
What are three things to avoid while separating?
1- mixing too vigorously
2- reactive solvents
3- high boiling point
33
what is fractional extraction?
extracting small amount multiple times rater than one big amount to reduce impurity.
34
What is gravity filtration?
physical separation of a solid from a liquid by passing it through filtration paper. Fluted filter paper is recommended.
35
what is vacuum filtatrion?
Vacuum filtration is performed with a Hirsch or Buchner funnel. A vacuum is created inside of the flask which creates suction to pull the filtrate through the filter paper. The filter usually has holes in it which are covered by the filter paper. The primary advantage is that it is faster than gravity filtration.
36
What is distillation used for?
separate two substances by simple distillation they must have boiling
37
2) A lab procedure instructs students to obtain an amine product by first acidifying the ether solution and then extracting multiple times with an aqueous solvent. If a student uses 1.5 M hydrochloric acid instead of the 2.5 M hydrochloric acid he is instructed to use by the lab manual, which of the following will result?
A) More ether molecules will be protonated and move into the aqueous layer, thus producing a better yield.
B) Fewer amine molecules will be protonated and move into the non-polar layer, thus producing a lower yield.
C) Fewer aqueous water molecules will form hydronium ions, decreasing the pH of the solution and thus producing a better yield.
D) Fewer amine molecules will be protonated and move into the aqueous layer, thus producing a lower yield.
Using a lower molarity acid will decrease the ability of the acid to protonate the amine and bring it into the aqueous layer (the desired effect). This will decrease yield. Answers A and C are eliminated because they predict an increased yield. Answer B is incorrect because charged amine molecules will be more soluble in the aqueous layer than in the non-polar layer. Answer D is thus correct.
38
What is chromatography?
| What is the first substance to elute?
separating one or more compounds by dissolving them in a mobile phase and then passing that phase through or across a stationary phase based on their polarity.
the more polar substance will stick to the stationary phase longer and the LEAST polar substance with be the first substance out of the tube.
39
what is paper or thin layer chromatography TLC ?
uses paper as stationary phase. TLC uses glass or plastic sheets coated with silica alumina, etc
40
what is rf?
Rf = distance traveled by component /distance traveled by solvent
41
If Rf = 0.9, is the substance in question polar or non-polar?
Given that Rf is a ratio of the distance traveled by the component over the distance traveled by the solvent. So a number close to one means that the polarity of the component is similar to that of the solvent. Because non-polar solvents are normally used, the component is therefore relatively non-polar.
42
During TLC, or paper chromatography, components will sometimes form an upward “smear” instead of forming a cohesive dot. Provide some possible causes of smearing.
Smears are usually caused when the solvent is unable to dissolve and carry the components as it moves up the paper via capillary action. This can be because too much of the sample was spotted onto the paper and the solvent could not dissolve the entire sample. It can also occur if there is too big of a difference in polarity between the sample and the solvent. If the polarities are too distant the solvent cannot dissolve the sample well enough to carry it. By a similar token, if they are too similar, the components may never come out of solution to form a spot and be carried all the way to the top of the paper.
43
What is column chromatography?
The mixture to be separated is passed through a column packed with charged glass beads, or some other polar matrix. The solution is collected in fractions at the bottom of the column (i.e., the collecting tubes are changed at regular intervals).
44
Which compounds will be eluted at the bottom of the column first?
In column chromatography, assuming a polar matrix, the most non-polar substances will elute first, followed by increasingly more polar substances.
45
What is ion exchange chromatography ?
The column or stationary phase is coated with cations or anions. The mixture is passed through and oppositely-charged ions adhere to the column. The target molecules can then be eluted by washing with a salt solution.
46
What is affinity chromatography?
Used to isolate a specific molecule or product based on a very specific affinity or binding interaction. For example, it may be that molecules in the mixture react via acid-base neutralization with molecules on the column. To elute the bound target molecules one must disrupt the binding interaction. This could be accomplished via a salt solution, but often requires a chemical reversal of the reaction that bound the target to the column.
47
What is gas chromatography?
A liquid is used as the stationary phase. The mixture is dissolved into a heated gas and then passed through the liquid. Various components reach the exit port at different rates based on 1) boiling point and 2) polarity. Only consider polarity if the two substances have almost identical boiling points.
--> there will be one peak for each unique compound in the mixture.
48
What causes one peak to be higher than another on a gas chromatograph?
The HEIGHT of the peak in a gas chromatograph is relative to the abundance of that component.
49
A student tests the melting point of his crystals to determine purity. Does a higher melting point indicate more purity or less?
Higher and sharper melting points indicate better purity. Impurities lower melting point. They also broaden the range across which the crystals melt.
50
Who does the double bond of a carbonyl (C=0) differ from the alkene double bond?
shorter and stronger because oxygen has greater electronegativity + Compared to two carbons, a carbon and an oxygen can get closer to one another because oxygen has a smaller atomic radius. This allows for more pi overlap and therefore a stronger bond.
51
What are key features of carbonyls?
1) Partial positive charge on the carbonyl carbon: This makes the carbon a good electrophile.
2) Alpha hydrogens: Hydrogens on the alpha carbon are surprisingly acidic—especially given that
alkane hydrogens normally CANNOT be removed.
3) Electron donating/withdrawing groups: The reactivity of a carbonyl with a nucleophile is dramatically affected by the presence of electron donating or electron withdrawing groups on the carbonyl carbon. Donating groups decrease the reactivity of the carbonyl carbon and
withdrawing groups increase its reactivity.
4) Steric hindrance: Bulky substituents attached to the carbonyl carbon decrease its reactivity.
5) Planar stereochemistry: The sp2 hybridized carbonyl carbon is planar and can therefore be
attacked from either side. When the two substituents on the carbonyl carbon are NOT identical, an addition reaction could therefore create both R and S enantiomers in a racemic mixture.
52
What are alpha hydrogens? what's an important characteristic?
hydrogens on carbon adjacent to a carbonyl carbon are acidic due to resonance stabilization of the conjugate base.
53
Rank the following structures in terms of increasing acidity of the alpha hydrogens:
a) CH3COCBr3, b) CH3COOH, c) CH3CONH2, d) CH3COCH3.
These structures differ in the substituents attached to the carbonyl carbon. An electron donating group on the carbonyl carbon will decrease its partial positive charge and thereby make it less able to stabilize the conjugate base. An electron withdrawing group will make the carbonyl better at stabilizing the conjugate base and therefore the strongest electron withdrawing group would indicate the strongest acid (because it produces the most stable conjugate base). Choice a) is the only electron withdrawing group, so it will have the most acidic alpha hydrogens. The weakest donating group of the other three is the methyl group on choice d). Amines (choice c) and hydroxyl groups (choice b) are both electron donating, but amines are better donating groups because nitrogen is less electronegative than oxygen. Therefore, in increasing order of acidity: c < b < d < a.
54
What are aldehydes and ketones that the MCAt may not use IUPAC name for?
These include formaldehyde (HCHO), acetaldehyde (CH3CHO), benzaldehyde (C6H5CHO), and acetone (CH3COCH3).
55
What are physical properties of ketones and aldehydes?
Aldehydes and ketones can act as hydrogen-bond acceptors when dissolved in water, with water acting as the hydrogen bond donor. Therefore, aldehydes and ketones will be far more soluble than alkanes. Finally, alcohols can hydrogen bond as both a donor and acceptor with water, so they will be the most soluble. Aldehydes and ketones do NOT hydrogen bond with one another, but they are both polar and will therefore have much higher boiling points than alkanes.
Finally, alcohols generally have the highest boiling points due to intramolecular hydrogen bonding.
These trends assume comparable molecular weight, chain length, etc. This is important because a small alcohol such as methanol is miscible with water, but dodecanol is considered insoluble. The boiling point of alkanes will be the lowest because their only intermolecular attraction would be van der Waals forces.
56
Aldehydes and Ketones can act as H- bonds ____ but NOT as H- bond ___
recipients; donors
57
what are major functions of aldehydes/ ketones?
electrophiles, their carbonyl carbon being attacked by nucleophile
58
Aldehydes and Ketones undergo ____
nucleophilic addition
59
Which is more acidic, the alpha hydrogen of a ketone, or the alpha hydrogen of an aldehyde? Provide a possible explanation.
The alpha hydrogen of an aldehyde is more acidic than a comparable alpha hydrogen on a ketone because the conjugate base in the case of the aldehyde is more stable. In an aldehyde, a hydrogen is attached to the carbonyl carbon, which is defined as neither a withdrawing group nor a donating group. However, in the case of a ketone an –R group is attached to that same carbonyl carbon and –R groups are weakly electron donating. This will decrease the magnitude of the partial positive charge on the carbonyl carbon in the ketone, making it less able to stabilize the negative charge of the carbanion in the conjugate base.
60
Why don’t aldehydes and ketones undergo substitution reactions?
they lack a suitable leaving group
61
Carboxylic Acids/ Amides/Esters/Anhydride
undergo nucleophilic substitution
62
What is keto- enol tautomerization?
process by which alpha hydrogens adjacent to an aldehyde or ketone becomes bonded to the carbonyl oxygen, while the double bond is switched from the carbon-oxygen bond to the bond between the carbonyl carbon and the alpha carbon.
63
Which is more stable, the keto or the enol tautomer? Why?
The keto and enol forms are in an equilibrium with one another that strongly favors the keto form at room temperature. The keto form is more stable because the sum of its bond energies is greater than the sum of the bond energies in the enol form.
64
It was previously stated that aldehydes and ketones cannot act as H-bond donors. An exception to this rule is 1,3-dicarbonyl compounds. They can act as hydrogen bond donors. Draw out a 1,3- dicarbonyl compound and propose an explanation.
A 1,3-dicarbonyl can undergo an intramolecular hydrogen bond when one of the carbonyls is in the keto form and the other is in the enol form. This significantly stabilizes the enol compared to a stand-alone enol. 1,3-dicarbonyls without also pointing out that they have ultra-acidic alpha protons on the carbon between the two carbonyl carbons—double resonance stabilization!
65
What are the steps to making an acetals/ hemiacetals?
1) An alcohol acts as the nucleophile, attacking the electrophilic carbonyl carbon and pushing the pi
electrons from the C=O bond up onto the oxygen.
2) The negatively charged oxygen is protonated to form an alcohol and the original alcohol is deprotonated to form an ether. This yields a hemiacetal if it was originally an aldehyde, or a hemiketal if it was a ketone.
3) The alcohol is protonated again to form the good leaving group water, and a second equivalent of alcohol attacks the central carbon as shown below.
4) Deprotonation of the second alcohol results in another ether, yielding an acetal if it was originally an aldehyde or a ketal if it was a ketone.
66
How do you protect ketones and aldehydes form reaction?
Ketones or aldehydes can be prevented from reaction with a nucleophile or base by conversion to an acetal or ketal (which are unreactive in all but acidic conditions). Any terminal diol with at least two carbons will work.
o STEPS:
1) One end of the diol acts as the nucleophile described in steps 1-2 above.
2) The other end of the diol acts as the “second equivalent of alcohol” described in steps 3-4 above.
3) Acidic conditions will return the acetal/ketal to the original aldehyde/ketone.
67
What is halogenation of an aldehyde to a ketone?
substitution of a Br, Cl, or I for one of the alpha hydrogens on an aldehyde or ketone.
STEPS:
1) A base abstracts an alpha hydrogen, leaving a carbanion.
2) The carbanion attacks a diatomic halogen.
68
what is aldol condensation?
condensation of one aldehyde or ketone with another aldehyde or ketone
STEPS:
1) A base abstracts an alpha hydrogen, creating a carbanion.
2) The carbanion will attack any carbonyl carbon in the solution.
3) The oxygen is protonated to form an alcohol.
69
What is an alpha, beta unsaturated carbonyl?
An aldehyde or ketone with a double bond between the alpha and beta carbons.
major contributor is one with no formal charges compared to a charge separation in the structure on the right. + think of it as an electrophile!
STEPS:
1) With the double bond between the alpha and beta carbons, the nucleophile attacks the beta carbon, pushing the double bond over one carbon and forcing the C=O electrons up onto the oxygen.
2) With a carbocation on the beta carbon, the nucleophile simply attacks the beta carbon directly.
Starting with either resonance form, the oxygen will get protonated to form an alcohol.
Note that the protonated oxygen is really just the enol form of a keto-enol tautomer.
70
What is carboxylic acid?
A carboxylic acid is any compound containing a carbonyl with a hydroxyl substituent on the carbonyl carbon (C=O)OH. - did ending
71
What are physical properties of carboxylic acids?
- high boiling points because they can form strong dimers involving two hydrogen bonds.
- mostly soluble in water and short COOH are also soluble in non polar solvents.
72
what are three key features of carboxylic acid?
1) resonance stabilization
2) induction - acidity based on stability of conjugate base
3) hydrogen bonding TWICE
73
What is equation for nucleophilic attack of carbonyl?
RCOOH + H2O RCOOH2+ + Nu:- RCONu + H2O
74
What is decarboxylation process?
The loss of a CO2 molecule from a beta-keto carboxylic acid, leaving behind a resonance-stabilized
carbanion. The process usually requires catalysis by a base.
The carboxylate ion usually retakes the hydrogen from the base, forming a keto-enol tautomer.
75
What is esterification?
| What is the process?
This is how triacylglycerols are formed: A glycerol undergoes esterification with three fatty acids.
RCOOH + ROH RCOOR + H2O
Reaction of an alcohol with a carboxylic acid to form an ester. You’ve probably realized by now that the hydroxyl group will never leave without being protonated first to form the “good leaving group water”; thus this reaction requires an acid catalyst.
Higher yields can be obtained by reacting an anhydride with an alcohol.
76
What are acid chlorides?
An acid chloride (a.k.a., acyl chloride) is any compound containing a carbonyl with a chlorine substituent on the carbonyl carbon.
77
What is formation of acid chlorides?
RCOOH + PCl3 RCOCl + H2O
Three reagents readily produce acid chlorides when added to carboxylic acids: PCl3, PCl5 and SOCl2.
Addition of chloride ion(Cl) to a carboxylic acid does NOT produce an acid chloride.
78
why are acid chlorides the most reactive of the carboxylic acid derivatives?
Their reactivity is due to:
1) the withdrawing power of the chlorine, which makes the partial positive charge on the carbonyl larger than normal, and 2) the fact that chloride ion is a superb leaving group.
79
Provide a reactant that will form each of the following when reacted with an acid chloride: a) an ester, b) an amide, c) an anhydride, d) a carboxylic acid.
a) ROH ; b) RNH2 ;
| c) RCOOH ; d) H2O
80
What are anhydrides?
An anhydride is a compound with two acyl groups connected to one another by a single oxygen. Viewed another way, an anhydride is an ester where the –R group is a carbonyl.
ending: -oic anhydride
81
What are properties of anhydrides?
Anhydrides are excellent electrophiles! The two carbonyl carbons are highly reactive to
nucleophiles because the leaving group is a resonance-stabilized carboxylate ion.
82
What are amides?
An amide is any compound containing a carbonyl with an amine substituent on the carbonyl carbon.
(benzoic acid --> benzamide).
83
What are properties of amides?
- most stable of all acid derivatives (carbonyl carbon is unreactive because NH2 is not a good leaving group).
- primary and secondary amides can hydrogen bond and are water soluble as long as they lack long alkyl chains. Tertiary amides cannot H-bond.
- resonance double bond character limits rotation
84
what is hofmann degradation?
primary amides (with only on hydrogen on the nitrogen) react in string, basic solutions of Cl2 or Br2 to form primary amines. The mechanism includes decarboxylation, and thus shortens the length of the carbon chain.
This reaction is important because it allows you to add an amine to a tertiary carbon.
85
What is an ester?
any compound containing a carbon with an OR group substituted on the carbonyl carbon.
- oate ending with R portion of -OR group named and placed in front of the name as is.
86
what are properties of an ester?
act as H bond recipients but NOT donors. not as soluble in water as acid and alcohols.
87
What are transesterification? What's process?
reaction of an existing ester with an alcohol, creating a different ester. also requires acid catalysis.
RCOORa + RbOH RCOORb + RaOH
88
What is saponification (hydrolysis of an ester)?
Hydrolysis of an ester to yield an alcohol and the salt of a carboxylic acid. o STEPS:
1) The hydroxide ion (NaOH or KOH) attacks the carbonyl carbon and pushes the C=O electrons up onto the oxygen.
2) The electrons collapse back down and kick off the –OR group.
3) Either the –OR group, or hydroxide ion, abstracts the carboxylic acid hydrogen, yielding a
carboxylate ion. This associates with the Na+ or K+ in the solution to form “soap.”
89
what is acetoacetic ester synthesis?
formation of a ketone from a B- kept ester
90
what are the step for acetoacetic ester synthesis?
STEPS:
1) A base abstracts the acidic alpha hydrogen, leaving a carbanion.
2) The carbanion attacks an alkyl halide (R-X), resulting in addition of the –R group to the alpha
carbon.
3) Hot acid during workup causes loss of the entire –COOR group.
91
what are familiar examples of inorganic esters?
triphosphase: ATP, GTP, UTP etc..
diphosphate: FADH2 and NADH
monophosphate: FMN, DNA, RNA
92
If a nucleophile is added to nay carboxylic acid or acid derivative, what will it attack ?
carbonyl carbon
93
What is ranking of acid derivative leaving groups (best to worst):
- Cl
- OH
- NH2
- OCOR
-Cl > -OCOR > -OH > -OR > -NH2
94
How do you determine the stability of the carboxylic acid derivative?
the better the leaving group, the more UNSTABLE the acid derivative
Amide>Ester>
CarboxylicAcid>Anhydride>
AcidChloride
95
what is an amine?
any organic compound that contains a basic nitrogen atom.
96
what are 4 properties of amines?
1) can act as either bases or nucleophiles: Primary or secondary amines usually act as nucleophiles and tertiary amines always act as bases (because they are too sterically hindered to act as nucleophiles).
2) Amine basicity decrease from tertiary to secondary to primary to ammonia due to the electron donating effects of the -R groups.
3) amines with four substituents act as electrophiles
4) amines are capable of hydrogen bonding.
97
Which functional group forms stronger hydrogen bonds, alcohols or amines?
Alcohols will form stronger hydrogen bonds because there is a greater difference in electronegativity between oxygen and hydrogen than there is between nitrogen and hydrogen. This greater dipole will create a stronger electrostatic attraction and therefore a stronger hydrogen bond.
98
___ synthesis is the most common human-body example of an amine acting as a nucleophile.
Protein
99
what is tautomerization?
an examine and mine interchange via a proton shift analogous to the veto enol- tautomerization
100
what is the synthesis of alkyl amines?
Formation of an alkylamine from an amine and an alkyl halide.
NH3 + CH3Br -> NH2CH3 + HBr
101
what are steps to alkyl amines?
STEPS:
1) Ammonia acts as a nucleophile, attacking the alkyl halide via SN2 and kicking off the halide ion.
2) The halide ion acts as a base, abstracting a hydrogen to quench the charge on the nitrogen.
o NOTE: This reaction results in many side products because the resultant amine is still a good nucleophile and can react again.
102
what is gabriel synthesis?
Formation of a primary amine from a primary alkyl halide; avoids the side products of alkyl
amine synthesis.
103
what is the step for gabriel synthesis?
The phthalimide ion, a reactive species with a full negative charge on the nitrogen, acts as a nucleophile, attacking the alkyl halide via SN2.
104
What is a reduction synthesis of amines?
Reduction of amides, imines, nitriles, and nitro groups via common reducing agents such as LiAlH4,
NaBH4, and H2/catalyst with pressure.
105
How do you reduce nitro groups?
can be reduced to the associated primary amine via all of the above listed reducing agents. Most O-Chem books focus on nitro groups being reduced by metals in HCl (M•HCl M=Fe, Zn, Sn)
106
How do you reduce nitrile groups?
can be reduced to the associated primary amine via all of the above listed reducing agents. Most O-Chem books focus on nitriles being reduced by LiAlH4
107
How do you reduce imines?
can be reduced to the associated primary amine via all of the above listed reducing agents. O-Chem books focus on imines being reduced by NaBH3CN or H2 and a Catalyst
108
how do you reduce amides?
reduce to the associated primary amine via LiAlH4 only
109
What is addition of amines to carbonyls (formation of examines and amines) ?
Amines add to aldehydes and ketones to form amines and examines.
110
What are the steps to adding amine to carbonyls?
STEPS:
1) The amine acts as a nucleophile, attacking the electrophilic carbonyl carbon.
2) The oxygen is protonated twice, creating the good leaving group water.
3) A base abstracts a hydrogen from the nitrogen and kicks off water in an E2 mechanism. This
forms either an imine or an enamine (depending on the substitution pattern of the nitrogen).
111
how do primary, secondary and tertiary amines react in formation of examines/ imines?
- Primary amines yield imines
- Secondary amines yield enamines
- Tertiary amines do not react.
112
What is order of acidity from least to most:
| water, aldehydes, water, carboxylic acid
aldehydes< alcohols< water< carboxylic acids (most electron withdrawing groups)
113
Which of the following structures will be the first intermediate formed during th e base catalyzed decarboxylation of a beta kept acid?
A) carbanion formed by abstraction of an acidic alpha hydrogen
b) resonance stabilized carbanion
c) an enolate ion, formed via removal of the R group from the ester
d) a carbon dioxide substituted ketone.
b) resonance stabilized carbanion regain it for kept enol tautomerization
114
which of the following pairs gives the most reactive and least react f the acyl derivatives, respectively?
a) acide, and acyl chlorides
b) amides and anhydrides
c) acyl chlorides and amides
d) anhydrides and amides
C; The reactivity order of the acyl derivatives is all determined by the quality of the acyl substituent as a leaving group. NH2- is the worst leaving group, therefore amides are the most stable and least reactive. Chloride ion is the best of the leaving groups so acyl chlorides are the most reactive. Anhydrides are very close behind acyl chlorides.
115
Which of the following events will create an absorbance peak on an H-NMR spectrum?
a) excitation of an electron to a higher energy level
b) nuclear energy transition
c) intramolecular vibrations
d) variations in the external magnetic field
B) H-NMR
a) UV
c) IR
d) /
116
Which will produce furthest upfield HNMR signal?
a) aldehyde
b) CBR4
c) Isopropyl alcohol
d) Tetramethylsilane
```
d
up shield (right)- upshielded
```
117
If an immune substituted benzene is reacted with LiaLH4, a primary benzyl amine can be produced. which of the following will be an intermediate formed during this reaction?
a) carbanion
b) carbocation
c) nitrogen anion
d) nitrogen cation
c
118
saponification involves which of the following transformations?
a) acid --. ester + alcohol
b) acid --> ester + acid salt
c) ester --> alcohol + acid salt
d) soap --> acid + ester
C- saponification is hydrolysis of ester
119
The first step in an acteoacetic ester synthesis in the addition of a strong base. the purpose of adding a base is to:
a) remove alpha hydrogen creating carbocation
b) remove alpha hydrogen creating carbanion
c) catalyze the reaction
d) attack the ester at the carbonyl carbon
b
120
A chemist is attempting to identify an unknown. He discovers that the unknown is soluble in dilute acid but not dilute base. The unknown most likely contains which of the following functional groups?
a) carbonyl
b) carboxylic acid
c) amine
d) ether
B) SOLUBLE IN ACID BUT NOT IN BASE = AMINE
121
c) something that is soluble in base, but not in acid, is SUSPECTED to be a ____?
carboxylic acid.
122
All of the following functional groups can be reduced to primary amine when reacted with NaBH4 EXCEPT:
I RNO2
II. R2C=NH
III. RCONH2
IV. RC=-N
III only because it needs stronger reducing agent as it's an amide.
123
for a carbon to decarboxylate, what position should the carbonyl be?
beta position
124
a student is attempting to identify an unknown in the lab. After testing multiple reagents she discovers that the unknown reacts with strong acids but not weak acids and with either strong or weak bases. Which of the following sets of functional groups are most likely found in the student's unknown?
a) amines and carboxyl acids
b) acid chlorides and esters
c) ammonium and carboxylic acids
d) amines and amides
A - The first piece of information in the question tells us that a functional group exists that will react with strong acids, but not weak ones. Amines (answers A and D) would fit this description, but an acid chloride (answer B) would not because acid chlorides are electrophiles. Answer C is false for the same reason; ammonium is an electrophile. Answer D is false because an amide is the one acyl derivative that will not react with anything at the carbonyl carbon and the hydrogens on the amide nitrogen are NOT acidic. Answer A is the best answer because an amine would indeed be expected to react with strong acids, but not weak ones and a carboxylic acid is strong enough to react with strong or weak bases.
125
which of the following species would be expected to have the greatest Rf values as measured form a paper chromatography?
a) hexane
b) phenol
c) aniline
d) diethyl ether
a- hexane- least polar species moves
