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Organic Chemistry Practice Problems

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Organic chemistry is not a fomulative science. It requires to generate the feeling about the natures of molecules and their reactions. The conceptual skills that can minimize the ability to make deductions. Even though most organic chemistry problems are qualitative, they are amenable to a logical, step-wise problem solving approach. The difficulty in solving problems in organic chemistry is partly due to the need to use more general, strategy based approaches.

Organic chemistry builds from the simple and straightforward to the complex and subtle. Organic molecules govern our life processes like metabolism, genetic coding and energy storage. All organic molecules contain carbon and to study organic chemistry is to study molecules made of carbon and to see what kinds of reactions they undergo and how they are put together.

Practice Problems with Answers

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Organic chemistry is a subset of chemistry concerned with compounds that contain the element carbon. Some of the organic chemistry practice problems are given below.

Solved Examples

Question 1: Intra¬†molecular hydrogen bonding occurs in cis-1,2-cyclopentanediol but not in the trans isomer. Why?¬†

Cyclopentanediol
Solution:
In cis-diol, the hydroxy groups are closer together while in the trans isomer they are too far apart. The hydroxy groups in the former structure thus can form hydrogen bond easily.

Question 2: o-Nitrophenol is steam volatile and less soluble than its other isomers. Why?
Solution:
Due to intramolecular hydrogen bond formation in o-nitrophenol, the intermolecular association is reduced, this makes it more volatile. Conversly because of intramolecular hydrogen bond, o-nitrophenol is incapable of forming hydrogen bond with water and is thus less soluble in water compared to the other isomers which can H-bond with water.

Solved Nomenclature Problems 

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The International Union of Pure and Applied Chemistry (IUPAC) has established a precise and comprehensive language for organic chemistry. With a solid understanding of organic nomenclature, its able to draw both the structure of any IUPAC name and give the IUPAC name for any structure given. Some of the organic chemistry nomenclature practice problems are given below.

Solved Examples

Question 1: Name the family for each compound listed below.
  1. Octanal 
  2. Cyclobutanone 
  3. Propyne

Solution:
The family for each compound is listed below.
  1. Aldehyde
  2. Ketone
  3. Alkyne


Question 2: Draw the structure of each of the following compounds. 
  • 4-chloro-1-butyne
  • (E)-2,3-dichloro-2-octen-1-ol
  • 3,3-dichloroheptanal
  • t-butyl methyl ether
  • 1,3-cyclobutadiene
  • 2-hydroxycyclopentanone
  • 4-methyl-2-cyclohexanone
  • 2-ethoxy-3-pentanone

Solution:
The structure of the compounds are given below. 

Structure of Organic Compounds

How to Solve Reactions Problems 

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Some of the organic chemistry reactions practice problems are given below.

Solved Examples

Question 1: Predict the major product of the reaction below.
Organic Reaction
Solution:
Heating an alcohol generally leads to loss of a water molecule. Multiple products (in this case, two) can be obtained depending on which H atom joins the -OH group to form water. The most stable product will be the most substituted alkene, which in this case is 2-methyl-2-butene. 

2 Methyl 2 Butene  

Question 2: The following reaction sequence is typical of SN1 reactions. Identify the rate limiting step.¬†
Sn1 Reaction
Solution:
The formation of a carbocation is always the rate limiting step for SN1 reactions. This step is the slowest to occur, and its rate determines the rate of the reaction. Step 2 is a nucleophile attack on the carbocation by ethanol. In step 3 a proton is lost from the protonated ether. Step 2 and 3 both occur very rapidly in solution and are not rate limiting steps. Step 1 is the rate determining step.