Reactions Types - Organic Chemistry
Card 0 of 276
For which of the following acid-base reactions will the equilibrium lie on the left side?
For which of the following acid-base reactions will the equilibrium lie on the left side?
The pKa value indicates how strong an acid is, and acid strength increases as pKa decreases. The side of a reaction with a lower pKa is going to dissociate more, pushing the equilibrium over to the other side. The equilibrium will thus lie on the side with the HIGHER pKa.
Since the pKa of acetic acid (4.76) is higher than the pKa of trifluoroacetic acid (0), the reaction will shift to the left to reach equilibrium.
The pKa value indicates how strong an acid is, and acid strength increases as pKa decreases. The side of a reaction with a lower pKa is going to dissociate more, pushing the equilibrium over to the other side. The equilibrium will thus lie on the side with the HIGHER pKa.
Since the pKa of acetic acid (4.76) is higher than the pKa of trifluoroacetic acid (0), the reaction will shift to the left to reach equilibrium.
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Rank these weak acids by decreasing 
(of the expressed hydrogens).
Rank these weak acids by decreasing
The governing principle regarding the prediction of 
values (relative to other compounds) is to assess the stability of the product formed by the release of a proton. The release of the alkyne hydrogen in compound III results in a carbanion, a highly unstable species, so it is expected that this compound is the least acidic and has the highest 
. Intuition serves well in this instance and we see that hydrogens bound to a triple bond have a 
value of around 25. The relative stabilities of the remaining compounds may be assessed in the same manner. Compound IV is the second weakest acid 
because the three methyl groups donate electron density such that if the oxygen is deprotonated, the resulting negative charge is destabilized. Methanol and water have a unique, non-intuitive relationship regarding their relative acidities. One would assume that water should be a stronger acid than other acids bound to alkyl groups (by the reasoning expressed for compound IV). This is the case for all alcohols except methanol, in which the delocalization of charge allowed by the increased molecular size outweighs the destabilization caused by electron donation. Thus methanol is a slightly stronger acid than water. This is evidenced in their 
values: 15.7 for water and 15.5 for methanol. The correct ordering of the given compounds is: III, IV, II, I.
The governing principle regarding the prediction of
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List the given compounds in order of decreasing basicity.
List the given compounds in order of decreasing basicity.
An easy way to consider relative base strengths is to consider the strength of the compounds' conjugate acids.The stronger the conjugate acid, the weaker the base. Water (compound IV) is the least basic of the compounds because its conjugate acid, 
is the strongest of the given compounds' conjugate acids 
. Carboxylate ions (compound III) are highly stabilized by resonance and predominate at neutral pH. The conjugate carboxylic acids readily donate protons (acetic acid: 
). Ammonia (compound I) has considerable basicity; binding a fourth hydrogen produces ammonium ion 
, which predominates at neutral pH 
Sodium propoxide (compound II) is a strong base, bearing a full negative charge on its oxygen. Its conjugate acid, 1-propanol, is a rather weak acid 
. Since its conjugate acid is the weakest (highest 
), sodium propoxide is the strongest base. Based on the previous observations the correct ordering of the compounds is: II, I, III, IV.
An easy way to consider relative base strengths is to consider the strength of the compounds' conjugate acids.The stronger the conjugate acid, the weaker the base. Water (compound IV) is the least basic of the compounds because its conjugate acid,
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A carboxylic acid has a pKa of 5. At a pH of 8, what is the ratio of salt to acid?
A carboxylic acid has a pKa of 5. At a pH of 8, what is the ratio of salt to acid?
Use the Henderson Hasselbalch equation:
Use the Henderson Hasselbalch equation:
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A.
B.
Which of the above molecules is expected to have a more acidic alpha-carbon, and why?
A.
B.
Which of the above molecules is expected to have a more acidic alpha-carbon, and why?
Molecule B will have a more acidic alpha-carbon because once the alpha proton becomes dissociated, the conjugate base will have relatively more stability than the conjugate base of molecule A.
When the alpha-carbon on molecule A loses it's proton, the conjugate base is not as stable. The reason for this is because the oxygen that is involved in the ester bond can contribute its electrons towards a resonance structure. Therefore, after the alpha-proton is lost, the alpha-carbon will have a negative charge that will be destabilized by the delocalized negative charge of the resonance structures.
Molecule B will have a more acidic alpha-carbon because once the alpha proton becomes dissociated, the conjugate base will have relatively more stability than the conjugate base of molecule A.
When the alpha-carbon on molecule A loses it's proton, the conjugate base is not as stable. The reason for this is because the oxygen that is involved in the ester bond can contribute its electrons towards a resonance structure. Therefore, after the alpha-proton is lost, the alpha-carbon will have a negative charge that will be destabilized by the delocalized negative charge of the resonance structures.
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Which of the following is the strongest acid?
Which of the following is the strongest acid?
From the start, we know we can eliminate answer choice 
because it is the only answer choice that is not a strong acid. Now we have three strong acids, but we have to determine which is strongest. To do so, we take the conjugate base of each strong acid to see which conjugate base is the weakest acid. Remember: weaker conjugate base means a stronger acid. 
is the largest ion of the bunch. Its large size allows it to better stabilize the negative charge and so it is the weakest (most stable) conjugate base. Because the weakest conjugate base leads to the strongest acid, 
is our correct answer.
From the start, we know we can eliminate answer choice
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Rank the given molecules in order of increasing pKa.
Rank the given molecules in order of increasing pKa.
Recall that the stronger an acid, the lower the pKa.
II (two fluorine atoms really close to 
has largest inductive effect, so bond is most weakened, and pKa is lowest)
V (one fluorine really close to 
has strong inductive effect)
I (one fluorine a little further away from 
has weaker inductive effect)
IV (no inductive effect)
III (alcohols are much less acidic than carboxylic acids, and it has the highest pKa of all)
Recall that the stronger an acid, the lower the pKa.
II (two fluorine atoms really close to
V (one fluorine really close to
I (one fluorine a little further away from
IV (no inductive effect)
III (alcohols are much less acidic than carboxylic acids, and it has the highest pKa of all)
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Which of the following sets of bases are listed from most basic to least basic?
Which of the following sets of bases are listed from most basic to least basic?
The correct ranking from most basic to least basic is:
The best bases are negatively charged, and the worst bases are positively charged (acidic). The stronger the base, the weaker (more stable) it's conjugate acid. An alkane is a very stable conjugate acid, which tells us that 
is the most basic of the set.
We know based on charge alone, that 
is more basic than 
but less basic than 
or 
.
We know that 
is more basic 
because the electronegativity of 
is less than that of 
. This means the lone pair of electrons on 
are held less tightly and more likely to pick up a proton.
The correct ranking from most basic to least basic is:
The best bases are negatively charged, and the worst bases are positively charged (acidic). The stronger the base, the weaker (more stable) it's conjugate acid. An alkane is a very stable conjugate acid, which tells us that
We know based on charge alone, that
We know that
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Which of the following sets of acids are correctly listed from most to least acidic?
Which of the following sets of acids are correctly listed from most to least acidic?
Remember that the strongest acids have the weakest conjugate bases. 
is more acidic than 
because iodine has a larger atomic radius than bromine. 
, 
, and 
are strong acids and should be at the beginning of the list. Alkanes are not acidic. Acetic acid is a weak acid (pKa =4-5).
Remember that the strongest acids have the weakest conjugate bases.
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Which side (left or right) of the following reaction is favored and why?
Which side (left or right) of the following reaction is favored and why?
The side of the reaction that is favored will have the acid with the higher 
, because the reaction goes (strong acid + strong base 
weak acid + weak base).
The side of the reaction that is favored will have the acid with the higher
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In an addition reaction
In an addition reaction
Addition reactions involve breaking one pi bond (double bond) and forming two sigma bonds in the product.
Addition reactions involve breaking one pi bond (double bond) and forming two sigma bonds in the product.
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A compound 
can be hydrogenated by platinum metal and hydrogen to give 
. How many rings and double bonds does the original compound have?
The original compound has no triple bonds.
A compound
The original compound has no triple bonds.
Hydrogenation of a double bond involves the bond breaking and a hydrogen being added to each carbon of that double bond. You can tell the number of double bonds by taking the number of hydrogens added and dividing it by 2.
6 added hydrogen divided by 2 is 3 double bonds.
A hydrocarbon with zero degrees of unsaturation and 
carbons has 
hydrogens. For every two hydrogens less than 
, there is one degree of unsaturation. After hydrogenation, our final product has no double bonds. After calculation, we see that it has two degrees of unsaturation. This means that it has two rings.
Hydrogenation of a double bond involves the bond breaking and a hydrogen being added to each carbon of that double bond. You can tell the number of double bonds by taking the number of hydrogens added and dividing it by 2.
6 added hydrogen divided by 2 is 3 double bonds.
A hydrocarbon with zero degrees of unsaturation and
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Which of the following reagents are required to convert 1-pentene to pentane?
Which of the following reagents are required to convert 1-pentene to pentane?
In order to convert an alkene into an alkane, we need a 
catalyst.
In order to convert an alkene into an alkane, we need a
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Ph = phenyl = benzene
Which reagent would work best to convert 
into 
?
Ph = phenyl = benzene
Which reagent would work best to convert
We can reduce the alkene here by simply adding two hydrogens with 
as a reagent.
We can reduce the alkene here by simply adding two hydrogens with
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Suppose that the given reactant, 1-hexene, is reacted with 
in the presence of ultraviolet light. Which of the following is the major product?
Suppose that the given reactant, 1-hexene, is reacted with
In this question, we're told that our starting material, 1-hexene, is being reacted with hydrobromic acid in the presence of ultraviolet (UV) light. To solve this, we need to consider how halogens add to alkenes, specifically in the presence of ultraviolet light.
First, it's important to note that UV light will cause the hydrogen and bromine atoms in 
to dissociate as free radicals. Because each of these atoms are electron deficient, they desperately want to react in order to fill their valence shells. And since the double bond in the alkene is electron dense, a reaction will occur between one of the electrons in this double bond and the free radical bromine.
The bromine radical adds to the alkene first at the 1-carbon in an anti-Markovnikov fashion. The reason it adds to this carbon (and not the 2-carbon) is because a secondary free radical is more stable than a primary free radical. Upon formation of this secondary radical, it will react with the hydrogen free radical in solution to generate the finished product, 1-bromohexane.
In this question, we're told that our starting material, 1-hexene, is being reacted with hydrobromic acid in the presence of ultraviolet (UV) light. To solve this, we need to consider how halogens add to alkenes, specifically in the presence of ultraviolet light.
First, it's important to note that UV light will cause the hydrogen and bromine atoms in
The bromine radical adds to the alkene first at the 1-carbon in an anti-Markovnikov fashion. The reason it adds to this carbon (and not the 2-carbon) is because a secondary free radical is more stable than a primary free radical. Upon formation of this secondary radical, it will react with the hydrogen free radical in solution to generate the finished product, 1-bromohexane.
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Which of the following electrophiles is matched incorrectlywith its catalyst needed for electrophilic aromatic substitution on a benzene ring?
Which of the following electrophiles is matched incorrectlywith its catalyst needed for electrophilic aromatic substitution on a benzene ring?
A catalyst is often required for an electrophilic aromatic substitution reaction. All reagents are paired with their correct catalysts except for 
. 
requires 
as a catalyst in order to react with benzene.
A catalyst is often required for an electrophilic aromatic substitution reaction. All reagents are paired with their correct catalysts except for
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What is the major product of the following reaction?
What is the major product of the following reaction?
The reaction shown is a Markovnikov addition of a hydracid (HX) across a double bond. According to Markovnikov's rule, the hydrogen gets added to the lesser-substituted carbon in the double bond, and the halide (in this case, 
) gets added to the more-substituted carbon. Thus, the correct answer is 
.
The reaction shown is a Markovnikov addition of a hydracid (HX) across a double bond. According to Markovnikov's rule, the hydrogen gets added to the lesser-substituted carbon in the double bond, and the halide (in this case,
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Classify the type of reaction given.
Classify the type of reaction given.
An addition reaction is a reaction in which the reactants react to combine and form one product. It is the opposite of an elimination reaction. In the reaction given, the reactants hydrochloric acid and ethylene combine to form the product 1-chloropropane.
An addition reaction is a reaction in which the reactants react to combine and form one product. It is the opposite of an elimination reaction. In the reaction given, the reactants hydrochloric acid and ethylene combine to form the product 1-chloropropane.
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Classify the type of reaction given.
Classify the type of reaction given.
An addition reaction is a reaction in which the reactants react to combine and form one product. It is the opposite of an elimination reaction. In the reaction given, the reactants 2-butene and molecular hydrogen combine to form the product butane.
An addition reaction is a reaction in which the reactants react to combine and form one product. It is the opposite of an elimination reaction. In the reaction given, the reactants 2-butene and molecular hydrogen combine to form the product butane.
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Classify the type of reaction given.
Classify the type of reaction given.
An addition reaction is a reaction in which the reactants react to combine and form one product. It is the opposite of an elimination reaction. In the reaction given, the reactants hydrochloric acid and propyne combine to form the product 2-chloropropene.
An addition reaction is a reaction in which the reactants react to combine and form one product. It is the opposite of an elimination reaction. In the reaction given, the reactants hydrochloric acid and propyne combine to form the product 2-chloropropene.
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