MIDTERM #3 PRACTICE TEST #1 - ASU · dependent, ca. 2 - 6 δ ... BuLi Ph PH3P O 1° bromide preferred + < < lowest highest B A C deleted deleted. Question 4 For each reaction a) Provide

Ian R. Gould

PRINTED FIRST NAME

Person on your LEFT (or Aisle)

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn

CHEM 234

PRINTED LAST NAME

H/H ~1.0

Eclipsing

H/Me ~1.4

Me/Me ~2.6

Me/Me ~0.9

Et/Me ~0.95

i-Pr/Me ~1.1

t-Bu/Me ~2.7

Gauche

Me/Et ~2.9

Interaction Energies, kcal/mol

ASU ID or Posting ID

Person on your RIGHT (or Aisle)

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C NR2

RC CRR2C CR2

Aromatic

CR OHO

C X

R NH2R OH

aminealcohol

3Y > 2Y > 1Y

020406080100120140160180200220

–H2C X

–H2C NR2

–OCH2–

01234567891011

C CHC HO

CR OHO

Aromatic Ar HAlkylmainly 8 - 6.5

C CH2

C CH3

O

3Y > 2Y > 1YAlkyl–OCH2–

CO

(δ, ppm)

variable and condition dependent, ca. 2 - 6 δ

R C N

O H C N

CN

CC

H

C ON H

C H

C N

O

HCO

CH

C CH

COR

ON H

C H

CO

O H

C O HO

CNR2

O

3000–3100

2850–2960

3300

broad ~3300

broad with spikes ~3300

2200

broad ~30001710

2200

1650

2720–28202 peaks

1735

1600–1660

1680

range of valuesbroad peak

small range usuallystrong

1600

CH

CH

C CHH

CH

CH

CH

CH

H

H

H

H

Approximate Coupling Constants, J (Hz), for

1H NMR Spectra

~7

~10

~2

~15~2

~8

Infrared Correlation Chart

NMR Correlation Charts

3000 200025003500 1500(cm-1)

THIS IS A CHM 234PRACTICE EXAM

MIDTERM #3PRACTICE TEST #1

the exam cover sheets look kind of like this

CHEMISTRY 234, MIDTERM #3 PRACTICE TEST #1 - 2 - NAMEQuestion 1 Give the IUPAC name for the following compounds. Be sure to use cis/trans, E/Z or R/S where appropriate.

(5R)-hydroxyhex-(3E)-enal

O

H

OH

* RH

12

34

56 aldehyde not numbered, is in position #1 by definition

trans-(5R)-hydroxyhex-(3)-enalOR

Question 2 Rank in order of increasing equilibrium constant for formation of an acetal with a brief explanation. Draw the expected acetal for one of the reactions (only), it does not matter which one.

H

O MeOH

H+ (cat.) H

MeO OMeA

acetalO MeOH

H+ (cat.)

MeO OMeB

acetalH

O MeOH

H+ (cat.) H

MeO OMeC

acetal

F F F F

MeOH is a weak L Base, reactivity of carbonyls (C=O) with Lewis bases depends upon substituents effects on the carbonyl carbon, B has two weakly donating alkyl groups attached to the carbon of the C=O and is thus the least reactive and has the smallest equilibrium constant, C has 2 F atoms that inductively withdraw electrons and increase reactivity and equilibrium constant

Question 3 Give the alkyl bromide and the carbonyl compound you would use to synthesize the following alkene in a Wittig synthesis and show all steps and reagents/conditions

PhPhBr PPh3

PhPH3P

BuLi

PhPH3P

O+1° bromide preferred

< <lowest highest

B CA

deleted

deleted

Question 4 For each reactiona) Provide the missing reagents/conditions or major organic products as appropriate, payattention to stereochemistry including racemic mixtures unless specifiedb) Unless otherwise indicated.....State whether the OVERALL reaction is Addition, Elimination, Substitution or RearrangementState whether the reaction is oxidation, reduction or neitherBriefly explain whether the a solution of the product would be optically active or not

b)

a)

CHEMISTRY 234, MIDTERM #3 PRACTICE TEST #1 - 3 - NAME

d)

c)

e)

O

Zn(Hg)

HCl, H2O**

H

H

H

H

O O H3O+ OOH OH

O

OCO/HClAlCl3

O

O

OHCH

1 Equiv. (CH3)2NH

HCl (cat.)

O

H

O ONMe2

ignore stereochemistry/optical activityignore oxidation/reductionignore addition/elimination etc

HO

OH

Na2Cr2O7/H2SO4O

O

OH

ignore stereochemistry/optical activityignore addition/elimination etc.

SUBSTITUTION (of 2xO for 2xH)REDUCTION

not optically active achioral meso compound

OXIDATION

ignore stereochemistry/optical activityignore oxidation/reduction etc.

SUBSTITUTION

ignore stereochemistry/optical activityignore oxidation/reductionignore addition/elimination etc

CHEMISTRY 234, MIDTERM #3 PRACTICE TEST #1- 4 - NAME

Question 5 Draw the complete arrow pushing mechanism for the following reaction. Indicate the Lewis acid/base at each step, and if they are also Brønsted acids bases. Add non-bonding electrons as necessary. Draw the ALL important resonance structure of the intermediates

O

LA

NHH3N

OH2NH

H3N

OH2N

H OTs

OHH2N

HTsO

OH2H2N

NH

NH HHH3N

LB

LA/BA

LB/BB

LB/BB

LA/BALA/BA

LB/BB

LB/BBLA/BA

TsOH (cat.)

NH3

note: the order of the first 2 steps in mechanism a) could be reversed!

Question 6 Rank the following in terms of increasing rate of reaction with PhMgBr. Give a BRIEF explanation and NAME the three functional groups

O

––– ––– –––< < CAB

this is reaction of a strong nucleophile/LB with a carbonyl C=O bond, which can be considered to be a small π-system, the carbonyl carbon in the ester B has a strong electron donating oxygen substituent on the carbonyl and a weak electrom donating methyl group, which decreases reactivity towards the LB/nucleophile, the ketone A has 2 weak alkyl donating substituents on the carbonyl carbon, the aldehyde C has only 1 weak alkyl donating group

B CO

O

H

O

A SD WDWDWD WD

ketone aldehydeester

WD = weakly donatingSD = strongly donating


CH3

CH3 CH3

CO2H

Br

Br

NO2 NO2

NO2

a)

HNO3 / H2SO4

Br2 / FeBr3

1. KMnO4 / –OH / heat2. H3O+

separate isomers

Question 7 Show how you would make the target molecules from the provided starting structures. Show all intermediate structures, do not show any mechanisms

b) OHO

BrO

BrOO OO

O

O

recall, H3O+ does not react with alkynes without Hg2+ as a catalyst

H3O+Na+

OHHOHCl cat.

PBr3

Na/NH3(l)

Question 2. For the Bronsted acid/base reaction below:a) Give the curved arrow-pushing in both directionsb) Draw a reaction energy diagram and include a drawing of the transition statec) Label the acids/bases and which are stronger and give a brief explanationd) Indicate which reaction is faster (left to right or vica versa) and on which side theequilibrium lies and which acid has the smaller and which the larger pKa

‡

reaction coordinate

energy

HHH H

H+ +H

weaker base weaker acid stronger acid stronger base

HH

H‡

the weaker base has lower energy electrons because the ion is aromatic, the stronger base is anti-aromatic if flat, or it it twists it may become non-aromatic, but will be less stable than the aromatic anion in any geometry

equilibrium on THIS side

slower

faster

larger pKa smaller pKa

Δ

1) draw the arrow-pushing that describes formation of the PROVIDED product2) How many electrons are involved in the reaction?3) FOR THE PROVIDED PRODUCT (which may or may not be allowed), wouldthe ring closing be disrotatory or conrotatory?4) FOR THE PROVIDED PRODUCT (which may or may not be allowed), wouldthe transition state be Hückel or Möbius?5) Is PROVIDED PRODUCT allowed or forbidden and why?

6 electrons

Möbius

Forbidden, the allowed product of a 6-electron electrocyclic ring closing reaction would proceed via an aromatic Huckel transition state and would be disrotatory, not Mobius/conrotatory

Conrotatory

Question 5. The purpose of this question is to determine whether the provided product is allowed or forbidden


Question 1 Give the IUPAC name for the following compound. Be sure to use cis/trans, E/Z or R/S where appropriate.

START OF PRACTICE TEST #2

O

H12

345 5-hydroxy-4-methylhept-(4E)-en-6-ynal

OH

67

Question 2 Rank the following in terms of increasing rate of electrophilic aromatic substitution, e.g., reaction with HNO3/H2SO4. Give a BRIEF explanation

OO

––– ––– –––< <CBAA

WO

O

OO

B

OO O

C

OO OW

D D D D D D

DDD W

the reaction is electrophilic aromatic substitution, as far as the central benzene rings are concerned, A has 2 D/activating groups and 2 W/deactivating groups, B has 3 D/activating groups and 1 W/deactivating group, C has 4 D/activating groups, C is thus fastest in electrophilic aromatic substitution

H3O+

cleave the 2 single bonds indicated by the dashed lines

O

N

add C=O here

NHO H

O

H

Question 3 Give the product of complet acid catalyzed hydrolysis of the following structure

deleted


Question 4 For each reactiona) Provide the missing reagents/conditions or major organic products as appropriate, payattention to stereochemistry including racemic mixtures unless specified

b)

a)

d)

c)

e)

C N1. Ph-MgBr

2. H3O+

O

(CH3)2NH

CF3CO2H (TFA) cat.(or any other organic acid catalyst)

O NMe2

1.

2. Zn/Hg/HCl/H2O

Cl

OAlCl3

MeO MeO

S S PhCH2 CH3

O

H H

1. BuLi2. CH3Br3. BuLi4. PhCH2Br5. H3O+

CH3OH

CH3O–

H

O

OCH3

HOH

(±)hemiacetal formed with base

deleted


Question 5 Give a full curved arrow-pushing mechanism for the following reactions, show where every proton goes to and comes from (no +H+/-H+) and indicate the Lewis and Bronsted acids/bases at each intermolecular step, include important resonance contributors for all intermediates, give the number of steps in your mechanism.

OO

O

OHHOO

H

H

HCl/H2OH

OO H

OHO OHO

O HHOH

OO

H

H OH

H

OH

O OHO

H

H

H

OH

O OHHOHOHO

H

H

LB/BB

LB/BB

LB/BB

LA/BA

LA/BA

LA/BA

LA/BA

LB

LA

SEVEN steps

OH ONaOH/H2O

OH

O OH

OH

LA/BA

LB/BB

LB/BBLA/BA

a)

b)


Question 6. Show how you would synthesize the target componds on the right from the starting compounds on the left. Show reagents and conditions, and the structures of important intermediate compounds. Do not show any (arrow pushing) mechanisms.

Br2, hν

Br BrMg

HO

O1.2. H3O+

Mg . THF

a)

a)

O

Br

OO

OO OO

MgBr

OH

O

OH

OH

HO OH/ H+ cat. (not H3O+)

HBr/ROORMg.THF 1.

O

2. H3O+

NaBH4/EtOH

meso compound

S Δ

Question 6) The ylide below undergoes an electrocyclic ring closure reaction

t-Bu

a) give the curved arrow-pushing that accounts for product formationb) draw the product, paying special attention to relative stereochemistry of any substituentsc) indicate the locations of any chiral (asymmetric) carbons atoms with the symbol, andstate whether it is racemic, a meso compound or achirald) give the NUMBER of electrons involved in the reactione) state whether the allowed reaction proceeds via a Huckel or a Mobius transition statef) state whether the allowed reaction proceeds via a conrotatory or a disrotatory ringclosing

t-Bu

conrotatory

*S t-But-Bu

*H H

*

Mobius4

*

non-aromatic

sp3

anti-aromatic4 electrons 4 electrons

anti-aromatic

8 electronsN

anti-aromatic

8 electrons

these electrons are in sp2 hybrid A.O.

Question 9) Classify the following structures as aromatic, non-aromatic or anti-aromatic, assume all structures are as flat as possible, AND give the number of electrons involved in the conjugated system

the reaction is antarafacial on the lower reactant because the cis-stereochemistry of the substituents becomes trans- in the product (this would not be included as part of the answer)




Question 2. Give a complete curved arrow pushing mechanism, and...1) Indicate the Lewis acid/Lewis base (LA, LB) at each step as appropriate, and whether theyare also Brønsted acids/bases (LA/BA, LB,BB), show where every proton comes from and goes to (no +H+/-H+)2) GIVE THE NUMBER OF STEPS IN YOUR MECHANISM

(4R)-hydroxyoct-(6Z)-en-2-one

OOH

12

34

56

R

78

*

HClOO

HO

O OOH

OO

HO

H

Cl–H

OO

OH

H–Cl

OO

HO

H

OO

HO

H

FOUR steps

Question 3) Classify the following structures as aromatic, non-aromatic or anti-aromatic, assume all structures are as flat as possible, AND give the number of electrons involved in the conjugated system

O

non-aromatic

sp36 electrons N

NH

aromatic6 electrons

these electrons are in sp2 hybrid A.O.s

H aromatic6 electrons

deleted

Question 3 For each reaction1) Provide the missing reagents/conditions or major organic products as appropriate

b)

a)


c)

d)

e)H

O

O H O

O

O

1 Equiv.HO OH

ignore stereochemistryTsOH (cat.)

O

O

OMgBr

Ph

H3O+

OH

Ph

O

N

Ph

H3O+O

PhH3N

HN CO/HCl

AlCl3Br

HN

Br

CHO

HN

BrOHC

and/or

H

H

Br2. BuLi3. O

1. PPh3deleted


Question 4 Rank the following in terms of increasing frequency of carbonyl stretching vibration in an IR spectrum. To solve this problem you will ened to draw minor resonance contributors and remember that stronger bonds vibrate with higher frequency)

H3C H

O

H3C

O

H3C NMe2

O

––– ––– –––< < ACBCA B

the more the minor resonance structure contributes to the overall structure, the more the C=O bond has single bond character, the lower the vibrational frequency....

H3C H

OH3C NMe2

O

H3C

O

H3C H

OH3C NMe2

O

CH3

O

H is not a donor, does not stabilize the minor resonance structure which is thus a small contributor to the structure

-NMe2 is the strongest donor, it stabilizes the minor structure resulting in a largest contribution to the structure of these three

-CH=CH2 is a weak donor, it is in the middle

Question 5 Give the product of the following reaction. Remember that D represents deuterium, an isotope of hydrogen, that is used to keep track of where hydrogen atoms go in chemical reactions. We did not cover this reaction class, but you should be able to work it out based on what you know about the mechanisms of these reduction reactions

CH3H3CCN 1. LiAlH4

2. D3O+

H

CH3H3CCN

HD

H

Δ

Question 9) The structure below undergoes an electrocyclic ring opening reaction (remember, D means deuterium, an isotope of hydrogen that is often used as a labelled hydrogen atom)

a) give the curved arrow-pushing that accounts for product formationb) draw the product, paying special attention to relative stereochemistry of any substituentsc) give the NUMBER of electrons involved in the reactiond) state whether the allowed reaction proceeds via a Huckel or a Mobius transition statee) state whether the allowed reaction proceeds via a conrotatory or a disrotatory ring closing

disrotatory

Huckel6

D

D

D

D


CO2H

SO3H

CO2H

KMnO4boil

SO3H2SO4

CO2H

SO3H

Br2FeBr3

Br

b)

O

Br

Br

OO

BrMg

OOOO

BrMgO

HO

OHO

OH

OHHOHCl cat.

Mg.THFO

H3O+

H2/Pd/C

a)

Question 6. Show how you would synthesize the target componds on the right from the starting compounds on the left. Show reagents and conditions, and the structures of important intermediate compounds. Do not show any (arrow pushing) mechanisms.


HOH

O

O

H3O+

a)

H HOH

O

O

H

O

O

HO

O

HHO

HO

O

H

OH

H

HO

HO

O

H

OH

H HOH

HO

OO

HH

HOCH2

HOO

H+CH2O

H

HO

HO+CO

H

H


N

NOH

NH

H

HO+ H

H

N

NOH

NH

H H OH

H

N

NOH

NHH

HOH

H

OHH

N

NOH

NHH

HOH

HO+ H

H

N

NOH

H3NH

OHN

NOH

OH

HOH

H

N

NOH

OH

uracilcytosinetautomer

cytosine is one of the pyrimidine bases in DNA, it can be converted into uracil. if this happens this can be a damage mechanism that could lead to mutation. Assume that this reaction occurs via the usual acid catalyzed mechanisms that we study in class, give a mechanism for formation of uracil from teh provided tautomer of cytosine

H3O+b)




O

H3-butyl-4-methyl-5-oxo-hex-(3E)-enal

213

456

O

Question 2 Rank the following in order of increasing equilibrium constant for formation of a hydrate. Give a BRIEF explanation

––– ––– –––< < BCAA B C

O

H3CO

OO

O2N

the reaction is addition of a weak nucleophile to the C=O group, A is least reactive since it has a strong donating group that can stabilize the carbonyl carbon via resonance, B has a withdrawing group that destabilizes the carbonyl carbon

δ+δ-

Question 3. Rank in order of increasing rate of reaction with –CN, give a BRIEF explanation

BA

<C A

B has donating group (oxygen) adjacent to the C=O, decreases reactivity towards nucleophilic attack, C has two electronegative groups adjacent to the C=O, inceasing reactivity towards nucleophilic attack

C

< B

O

O

O

F F

O

(fastest) (slowest)

deleted

Question 4. For each reaction.1) Provide the missing reagents/conditions or major organic products as appropriate2) Pay attention to stereochemistry including racemic mixtures unless specified

b)

a)


c)

d)

e)

OH+ cat.

(CH3)2NHN enamine

Br2 / FeBr

F3C F3C Br

KOH/heat

OBr HON2H4

N

NH2

OHCl (cat.)

H

OO

OHO O OHH3O+


Question 5. Show how you would synthesize the target compound on the right from the starting compound on the left. Show reagents and conditions, and the structures of important intermediate compounds. Do not show any (arrow pushing) mechanisms.

a)

HNO3 / H2SO4

Br2 / FeBr3

O

O

NO2

NO2NH2

Br

Cl2 / AlClr3

O

Cl/ AlCl3

Zn(Hg)/HCl/H2O

separateisomers

NH2

Br

Cl

bit of a trick here, the Clemmensen reduction would probably also reduce the -NO2 to the

required -NH2 making the next step (H2/Pd/C) unnecessary, but you would not lose points for

the separate reduction of the -NO2

H2/Pd/C

NH2O

O

H

OH

O O

HOH

Ph

O

HOH

Ph

N

OH OHHClcat.

1 Equiv

1. PhMgBr2. H3O+

CH3NH2HCl (cat.)

b)


O

O

b)

H HOH

O

OH

O

HO

O

HOO

H H

HO

H

O

HOOH

H HOH

O

HOOH

H

OH

HO OHH3O+

OH

HO

H

O+

O

HO


a)

O

H3O+

O

OH

+H

OH O

H

H

OH

H

H HO+

H••

OH

H••

H HO+

H

+ +

OH

H+

OH

H••


––– –––

Question 7 Rank in order of increasing rate of reaction with a Grignard reagent, giove a brief explanation in terms of nucleophiles and electrophile stregth and tthe factors that control these in this context.

––– –––< <<D A CB

F3C H

O

H H

O

H3C CH3

O

H3C H

O

DCBA

In these reactions the Grignard is the Lewis base and the carbonyls are the Lewis acid, the stronger the Lewis acid the faster the reaction

the carbonyl carbon in D has two weak donating -CH3 groups attached, which decerases the electrophilicity, this reaction is slower than A (one donating group) which is slower than B (zero donating groups)

C is fastest of all, the -CF3 is electron withdrawing, which incerases the electrophilicity of the carbonyl carbon

Question 8. Rank in order of increasing rate of electrophilic aromatic substitution at the carbons indicated by the arrows. Give a BRIEF explanation.

B

C

A

slowest fastest

< <

CN

NH

CH3

D

<D B C A

Reaction at both A and C is faster than at B and D, because both are activated by strong (amine) and weak (aryl) donating groups on the ring. Reaction at A is activated more than at C because the strongest donating group activates more. Reaction at B and D is deactivated by the by strongly withdrawing nitrile group, but D is deactivated more than at C.

Documents

MIDTERM #3 PRACTICE TEST #1 - ASU · dependent, ca. 2 - 6 δ ... BuLi Ph PH3P O 1° bromide preferred + < < lowest highest B A C deleted deleted. Question 4 For each reaction a) Provide