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Chem 311
1st semester Organic Chemistry
84
Organic Chemistry
Undergraduate 3
11/24/2012

Additional Organic Chemistry Flashcards

 


 

Cards

Term

Reaction of a terminal alkyne with 2 equivalents of HCl

 

Definition

forms a geminal dichloride with the two chlorine atoms on the  second carbon, i.e.

R-C(Cl)2CH3

Term
Deprotonation of a terminal alkyne occurs with  ______ and forms an ________
Definition

a strong base such as NaH or NaNH2

 

an acetylide anion, which is an excellent nucleophile

Term
Hydration of a terminal alkyne with H2SO4/HgSO4
Definition
gives an aldehyde because it forms an enol RCH=CH(OH) that tautomerizes to the more stable keto form 
Term
Hydration of an internal alkyne with H2SO4/HgSO4 gives
Definition
a ketone since it initially forms an enol (RCH=CR(OH)) which tautomerizes to the more stable keto form.
Term
Markovnikov addition of HBr to an unsymmetrical alkane
Definition
results in the bromine added to the more substituted carbon atom because the most stable carbocation is an intermediate.
Term
Markovnikov addition of water to an unsymmetrical alkene (hydration)
Definition
results in the formation of an alcohol, with the OH group going on the most substituted carbon atom due to the formation of the most stable carbocation.
Term
Anti-Markovnikov hydration of an unsymmetrical alkene with BH3 followed by H2O2/OH-
Definition
forms an alcohol where the OH group is on the less substituted carbon. This does not proceed through a carbocation intermediate, but is a result of the syn addition of BH3 to the double bond. Boron goes on the less substituted carbon because of steric effects and is replaced on the same carbon by H2O2/OH-
Term
Addition of the elements of OH and a halide to an alkene (halohydrin formation) occurs when an alkene is contacted with
Definition
a halogen (Br2 or Cl2) and water. Anti addition occurs because the water does a backside attack on the halonium ion intermediate.
Term
Halogenation of an alkene occurs via _____ addition because __________
Definition
anti addition because of the formation of the intermediate halonium ion intermediate. Backside attack occurs because of steric effects.
Term
Structure of pyridine
Definition
[image]
Term
Structure of acetylene
Definition
[image]
Term

[image]

 

What is type of reaction is this?

Definition
Bromination; note anti-addition (trans)
Term
Draw the halohydrin reaction product of cyclohexene with bromine and water.
Definition

[image]

 

Trans addition because of intermediate bromonium ion and backside/underneath attack of the nucleophile.

Term
Define constitutional isomers
Definition
have the same molecular formula but differ the way the atoms are connected
Term
Define Stereoisomers
Definition
have the same molecular formula and the same atom-to-atom connections but differ in the way the atoms are oriented in space.
Term
Define Enantiomers
Definition
are stereoisomers that are non-superimposable mirror images
Term
Diastereomers
Definition

occur when you have two or more stereocenters. One of the pairs of stereocenters has the same configuration and the other pair has the opposite.

 

RR   and    RS

 

If you had RR and SS, they would be enantiomers

Term

What is the relationship of the molecules?

 

[image]

Definition
Constitutional isomers
Term

What is the realtionship of the molecules?

 

[image]

Definition
They are stereoisomers; specifically diastereomers - one of the stereogenic centers is the same and one is different
Term

What is the relationship of these molecules?

 

[image]

Definition
Enantiomers
Term

What is the configuration (R vs S) of the stereoisomers?

[image]

Definition

[image]

The top one is R, the bottom is S

Term

What is the stereochemical configuration (R or S) of this molecule?

 

[image]

Definition
R
Term

Which of the following molecules will not have a dipole moment?

 

H2O

NH3

CH3CH3

CHCl3

Definition

 

CH3CH3

Term

Which of the following molecules has a dipole moment?

 

CH4

CCl4

CH2Cl2

Cl2C=CCl2

Definition
CH2Cl2
Term

What is the molecular geometry of formaldehyde?

 

CH2O

Definition

trigonal planar

 

[image]

Term

What is the hybridization of the carbon in formaldehyde?

 

[image]

Definition

 

sp2

Term

Name the functional groups:

 

[image]

Definition

[image]

 

    alcohol        aldehyde        ketone         carboxylic acid

 

Remember "R" is any carbon group 

Term

Specify the type of alcohol (primary, secondary, etc):

 

[image]

Definition

 

[image]

     primary         tertiary        secondary     primary 

Term

What functional group is present in coniine?

 

[image]

       A.  amide     B.  imine      C. amine      D. nitrile

Definition
C. amine
Term

Which of the following is classified as a protic solvent?

 

A.  ethanol

B.  ethyl ether

C. Dichloromethane

D. DMSO

Definition

 

Protic solvents have OH groups. The only one in the list is A. Ethanol (CH3CH2OH)

 

Term

Which of the following is a polar aprotic solvent:

 

A. water

B. benzene

C. acetone

D. methanol 

Definition

Polar aprotic solvents have polar bonds but no OH groups.

 

The only polar aprotic solvent in the list is C. acetone.

 

Note: benzene is an aprotic solvent but it is not polar

Term

Classify the following reaction as an addition, substitution, elimination or acid-base reaction:

 

[image]

Definition

 

Substitution reaction

Term

Classify the following reaction as an addition, substitution, elimination or acid-base reaction:

 

[image]

Definition
Addition reaction - water is added across the triple bond to form the enol which rearranges to the more stable keto form.
Term

What is/are the enol form/s of the ketone?

 

[image]

Definition
 A and D are the enol forms of the ketone
Term

Which of the following cations is the most stable?

 

[image]

Definition
B. is the most stable (tertiary cation)
Term

Which of the following cations is least stable?

 

[image]

Definition
A is least stable (primary cation).
Term

Which of the following cations has unusual stability due to resonance?

 

[image]

Definition

D.  has resonance stabilitzation which makes it more stable than a primary cation.

 

[image]

Term

If the energy level of the products is greater than that of the reagents, the reaction is

 

A.  exothermic

B. endothermic

Definition

B. endothermic

Energy must be added to the reaction

Term

If the energy level of the products is less than that of the reactants, the reaction is said to be

 

A. Exothermic

B. Endothermic

Definition
A. Exothermic
Term

If a reaction such as the one below gives products that have undergone skeletal rearrangements, what can you conclude about the most likely mechanism of the reaction?

 

[image]

Definition
That an intermediate carbocation has formed and undergone rearrangement to form a more stable carbocation (2o to 3o)
Term

Which of the following is the best nucleophile?

 

[image]

 

                  A.                     B.                    C.

Definition

 

B. because is has a negative charge (vs A) and it is not stabilized by resonance (vs C).

Term
True/False: An alcohol must be transformed into a good leaving group prior to undergoing substitution or elimination reactions.
Definition
True
Term

What reagent is needed for the following reaction?

 

[image]

Definition
Anti-Markovnikov addition of water to a double bond is a result of treatment with borane (BH3) followed by alkaline hydrogen peroxide (H2O2/OH-).
Term

What reagent is needed for the following reaction?

 

[image]

 

Definition
Markovnikov addition of water to an alkene can be affected by aqueous sulfuric acid (H2O/H2SO4)
Term

Which reagent would affect the following transformation?

 

[image]

A. CH3OH/H2SO4

B. CH3O-Na+/THF

Definition

A. CH3OH/H2SO4

 

In order for the nucleophile to end up on the most substituted carbon, you need conditions that favor the formation of a carbocation, like SN1-type conditions. The oxygen atom is protonated and that facilitates opening of the epoxide ring on the side that will result in the most stable carbocation (most substituted carbon).

Term

Which reagent would affect the following transformation?

 

[image]

 

A. CH3OH/H2SO4

B. CH3O-Na+/THF

Definition

B. CH3O-Na+/THF

 

In order for the nucleophile to end up on the least substituted carbon of the epoxide, you need to have SN2-like conditions; a strong nucleophile that is influenced by steric effects and will attack the least-substituted carbon.

Term

Determine the product:

 

[image]

Definition
[image]
Term

Determine the product:

 

[image]

Definition
[image]
Term

The pKa of benzoic acid is 4.2 and the pKa of methanol is 15.5. Consider the following equilibrium. Which would be favored, the products or the reactants?

 

[image]

Definition
The equibrium favors the formation of the reactants. The stronger acid (benzoic acid, pKa 4.2) has the weaker conjugate base. It is not strong enough to remove a proton from methanol. In other words, acid-base equilibria favor the formation of the weaker of the two acids (higher pKa).
Term

Name the three functional groups in the molecule:

 

[image]

Definition
ketone, alcohol, alkyne
Term

Name the four functional groups in the molecule:

 

[image]

Definition
ester, thiol, amine, benzene ring
Term

Which is the most stable rotational conformation of 1,2-dichloroethane?

 

[image]

Definition

B.  The chlorines are farthest apart (staggered, anti)

 

Note that structure C is the wrong molecule; it is 1,1-dichloroethane.

Term

Which is the least stable rotational conformation of 1,2-dichloroethane?

 

[image]

Definition
D is the least stable; the chlorine atoms are virtually on top of each other, and the conformation is eclipsed.
Term

Which is the more stable conformation of methyl cyclohexane?

 

[image]

Definition
The equatorial isomer (on the left) is more stable; the axial conformation has more crowding due to the other axial hydrogens.
Term

A substituted bromo cyclohexane is subjected to potassium t-butoxide and the following three products are found. No rearrangements have occured. What is the starting material?

 

[image]

Definition

[image]

Note that there are three different beta protons on this structure; elimination leads to three different products.

Term

A subsituted bromocyclohexane is subjected to elimination conditions (potassium t-butoxide) and gives three products. Which is the major product formed?

 

[image]

                A.                    B.                  C.

Definition
Product A is formed the most; the alkene is more highly substutitued; Zaitsev's rule.
Term

A primary alkyl halide reacts with a strong nucleophile. What is the most likely mechanism?

 

SN1     SN2      E1      E2

Definition
SN2
Term
A tertiary alkyl halide reacts with a strong, bulky base in a polar aprotic solvent. What would be the result and the likely mechanism?
Definition
An elimination reaction would  occur since a strong base or nucleophile favors an SN2 or E2 reaction. A tertiary alkyl halide is too sterically hindered to undergo an SN2 reaction, so only E2 elimination occurs.
Term
A primary alkyl halide is contacted with a strong, sterically hindered base. What is the most likely result?
Definition
Elimination reaction via an E2 mechanism since a strong sterically hindered base is a lousy nucleophile.
Term
A secondary alkyl halide is reacted with a weak nucleophile/weak base. What is the likely result?
Definition
A mixture of SN1 and E1 products.
Term
A secondary alkyl halide reacts with a strong base such as CH3CH2O-. What is the likely result?
Definition
A mixture of SN2 and E2 products since a strong base is also a strong nucleophile.
Term
What is the result if a stereogenic center (chiral carbon) is subjected to SN2 reaction conditions?
Definition
Inversion of the stereocenter will occur.
Term
What is the result if a stereocenter is subjected to SN1 reaction conditions?
Definition
Racemization of the stereocenter will occur.
Term
Which reaction mechanism, SN1 or SN2 would exhibit second order kinetics?
Definition
SN2 - it is bimolecular
Term

Which reaction mechanism, E1 or E2, would exhibit first order reaction kinetics?

 

Definition

 

 

E1

Term
Which reaction mechanism, SN1 or SN2, is favored by polar, protic solvents?
Definition
SN1
Term
Which reaction mechanism, E1 or E2, is favored by polar aprotic solvents?
Definition
E2
Term

What is the product of the following reaction:

 

[image]

Definition
[image]
Term

What is the name of the following reaction?

 

[image]

Definition
The Williamson ether synthesis.
Term
What reagent would be used to convert a primary alcohol to an alkyl chloride?
Definition
SOCl2/pyridine
Term
What reagent could be used to convert a primary or secondary alcohol to an alkyl bromide?
Definition
PBr3
Term

What reaction conditions would work the best for the transformation of 2-bromopentane to 1-pentene?

 

A. KOC(CH3)3/ HOC(CH3)3

B. NaOH/H2O

C. Na/NH3

D. H2/Pd/C

E. None of the above

Definition

 

A. KOC(CH3)3/ HOC(CH3)3

 

A strong, bulky non-nucleophilic base is best for elimination reactions.

Term

What is the stereochemical configuration (R vs S) of this molecule?

 

[image]

Definition
R
Term

Order the following substituents according to the Cahn-Ingold-Prelog priority system

 

A.  Cl

B.  Br

C.  CH3

D.  CH2OH

E. CO2H

Definition
Br>Cl>CO2H>CH2OH>CH3
Term

Name the alkene, including E/Z

 

[image]

Definition
(3E) 4-ethyl-3-methyl-3-heptene
Term

Name the alkene, including E/Z

 

[image]

Definition
(4Z) 4,5-diethyl-4-octene
Term
What is the result if an alkyne is reacted with two equivalents of strong acid (i.e. HBr)?
Definition

[image]

Two equivalents of acid are added in a Markovnikov fashion to give a geminal halide

Term
How can you produce a cis-alkene from an alkyne?
Definition

Use Lindlar's catalyst

 

[image]

Term

What is the result if you react an alkyne with sodium in liquid ammonia?

 

 

Definition

[image]

You get a trans- alkene

Term

What is the product of the following reaction?

 

[image]

Definition

[image]

Reduction of an alkyne with hydrogen and a metal catalyst takes the  triple bond all the way down to the alkane. It goes through the cis double bond but doesn't stop.

Term

Which is the product of hydrogenation of this double bond?

 

[image]

Definition

[image]

Hydrogenation is always syn addition, so this product has to have both methyl groups "cis".

Term

What reagent is needed to affect the following transformation?

 

 [image]

Definition

LiAlH4 or NaBH4

will add hydride (H-) in an SN2 reaction - hydride is the nucleophile and replaces the halide just like other nuclophiles.

 

Term

What is the product of the following reaction?

 

[image]

Definition

[image]

 

LiAlH4 adds Hydride (H-) as a nucleophile to the epoxide on the least substituted carbon.

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