All Organic Chemistry Resources
Example Questions
Example Question #1 : Organic Chemistry
What is the IUPAC name of the given molecule?
None of these
2,2,4-trimethyloctane
4,6-dimethyl-6-ethylpentane
3,3,5-trimethyloctane
3,3,5-trimethylnonane
3,3,5-trimethyloctane
The longest carbon chain that can be formed is eight carbons. The base molecule is octane.
Using IUPAC rules, substituents should have the lowest possible numbers; thus, we start counting carbons from the right side rather than the left. If you count from the correct side, there are two methyl groups on carbon 3 and one on carbon 5. Thus, the name of the moleculue is 3,3,5-trimethyloctane.
Example Question #1 : Reactions By Product
How could you brominate the compound?
Hydrobromic acid
Bromine gas
None of these
Bromine and peroxides
Bromine and UV light
Bromine and UV light
The given molecule is an alkane. The only way to brominate an alkane is with bromine gas and UV light. The energy from the light serves to creat two radical bromines. These radicals are capable of bonding with alkanes. If the given compound were an alkene, either hydrobromic acid or bromine and peroxides would work.
Example Question #1 : Help With Alkane Synthesis
Predict the absolute configuration about the double bond formed in the given E1 reaction.
No elimination reaction would proceed
Z
E
Racemic Z/E
E
Unlike E2 reactions, in which hydrogen abstraction occurs simultaneously with the dissociation of the leaving group (limiting the configuration of the reaction's product), E1 reactions occur in two distinct steps. The slow rate-determining step that must first occur is the dissociation of the leaving group. Leaving behind a carbocation intermediate, it is often necessary to consider possible carbocation rearrangements that would stabilize the positive charge.
In this case, no such rearrangement is favorable as their are no locations of greater stability available.
However, what must be considered is that the intermediate is free to orient itself in its most stable conformation prior to the formation of the double bond in the second step. As a result, the E product (the larger substituents are on oriented opposite one another with respect to the double bond) is yielded primarily.
Example Question #2 : Reactions By Product
Which reagents are required to carry out the given reaction?
To carry out this reaction, we need to create a radical as an intermediate, which is an unpaired electron. We do so by introducing , UV light, and heat to the 1-methyl cyclohexane. The light and the heat react with the
to break the bond and create two radical bromine atoms. One of the radical bromine atoms removes a hydrogen from the carbon on the 1-methyl cyclohexane that is most substituted, and a radical carbon is formed. Finally, the second radical bromine reacts with the radical carbon to form the final product.
Example Question #1 : Help With Alkene Synthesis
What is the IUPAC name of the given diene?
5-chloro-3,5-dimethyl-1,6-heptadiene
None of these answers
3-chloro-2,5-dimethyl-2,6-heptadiene
3-chloro-2,5-dimethyl-1,5-heptadiene
5-chloro-3,6-dimethyl-1,5-heptadiene
5-chloro-3,6-dimethyl-1,5-heptadiene
You must begin counting the carbons so that the first functional substituent has the lowest possible number. In this case, C1 is connected to C2 by the double bond, meaning we start counting from the left.
The longest carbon chain is seven carbons so the parent molecule is heptane. With this numbering, there are methyl groups on carbons 3 and 6 and a chlorine on carbon 5.
Substituents are named in alphabetical order and two double bonds result in a diene. Thus, the correct answer is 5-chloro-3,6-dimethyl-1,5-heptadiene.
Example Question #1 : Help With Alkene Synthesis
What is the value of from Huckel's rule for the given aromatic compound?
Huckel's rule states that an aromatic compound must have delocalized electrons. The electrons in each double bond are delocalized for this molecule. There are nine double bonds, and thus eighteen delocalized electrons.
If 4n+2=18, then n=4.
Example Question #2 : Help With Alkene Synthesis
Which of the following reagents would convert butanone into 2-butene?
1.
2. Heat/
1.
2. Heat/
1.
2.
1.
2. Heat/
Two sets of reagents are required to convert butanone into 2-butene. First, we use to reduce the butanone into a 2-butanol. Second, we use heat and acid to dehydrate the butanol and yield the final desired product.
1. ; 2. Heat/
may seem like an acceptable answer choice. However, note that the Grignard reagent converts the butanone into a tertiary alcohol, rather than a secondary alcohol as needed.
Example Question #1 : Help With Alkene Synthesis
2-butone is reacted with to form a product. That product was then heated in acid
to form a final product. What is the final product?
2-butene
2-butanol
None of these
Butane
2-butene
2-butone is a carbonyl compound that can readily be reduced by into a secondary alcohol, 2-butanol. When 2-butanol is heated in acid, we get dehydration, which leads to 2-butene.
Example Question #4 : Help With Alkene Synthesis
What is the reactant of the given reaction?
This is an addition reaction with 3 products. The unknown reactant reacts with and gives those three products. Addition reactions begin with double bonded compounds and so these electrons are used to react with some reagent
. One needs to work backwards to figure out how something was formed and in this case, there are mechanistic pathways, and one of the pathways involves a hydride shift. These 3 products often exist in different concentrations after the reaction.
Example Question #1 : Reactions By Product
Which of the following reagents can be used to create a E alkene from an alkyne?
None of these
Metallic sodium in liquid ammonia creates solvated electrons which can convert an alkyne to an E alkene. The same will not happen when sodium is combined with water, where sodium reacts violently to create sodium hydroxide and hydrogen gas. Lindlar's catalyst is a poisoned catalyst used to form alkenes from alkynes, bud results in a Z conformation. Without the poisoned catalyst, an alkane will be formed.
All Organic Chemistry Resources
![Learning Tools by Varsity Tutors](https://vt-vtwa-app-assets.varsitytutors.com/assets/problems/og_image_practice_problems-9cd7cd1b01009043c4576617bc620d0d5f9d58294f59b6d6556fd8365f7440cf.jpg)