Problem 43 - General Chemistry

Question

Give the condensed structural formula for each of the following compounds. a 3-ethyl-2-pentene b 4 -ethyl-2-methyl-2-hexene

Step-by-Step Solution

Answer

3-ethyl-2-pentene: CH3-CH=C-C2H5-CH3; 4-ethyl-2-methyl-2-hexene: CH3-CH=C(CH3)-CH2-CH(C2H5)-CH3

Step 1: Identify the Main Chain

For 3-ethyl-2-pentene, the main chain is a pentene, which means there are 5 carbon atoms, and a double bond is present starting at the second carbon. Hence, the main chain is C5H10 with a double bond between C2 and C3.

Step 2: Attach the Substituents

The '3-ethyl' indicates that there is an ethyl group (C2H5) attached to the third carbon of the main chain. Therefore, the main compound has the ethyl group at carbon 3.

Step 3: Write the Condensed Formula for 3-ethyl-2-pentene

Start with the longest chain and include the alkyl group. The condensed structural formula becomes: CH3-CH=C-C2H5-CH3.

Step 4: Identify the Main Chain for the Second Compound

For 4-ethyl-2-methyl-2-hexene, the main chain is hexene since there are 6 carbon atoms in a row with a double bond at carbon 2, turning it into C6H12.

Step 5: Attach the Substituents

The '4-ethyl' signifies an ethyl group (C2H5) at the fourth carbon, and '2-methyl' signifies a methyl group (CH3) at the second carbon.

Step 6: Write the Condensed Formula for 4-ethyl-2-methyl-2-hexene

Combine the main chain with its substituents, resulting in the condensed formula: CH3-CH=C(CH3)-CH2-CH(C2H5)-CH3.

Key Concepts

Understanding Organic Chemistry

Organic chemistry is a branch of chemistry focused on carbon-containing compounds. Carbon is unique due to its ability to form stable bonds with many elements, including hydrogen, oxygen, and nitrogen. This property allows for the creation of diverse and complex molecules.

One major category in organic chemistry is hydrocarbons, which only contain carbon and hydrogen atoms.

• Alkanes are saturated hydrocarbons with single bonds only.
• Alkenes, like those in your exercise, contain one or more double bonds between carbon atoms, making them unsaturated.
• Alkynes are unsaturated as well but contain triple bonds.

Organic compounds play numerous roles in daily life, from fuels and plastics to pharmaceuticals and biological systems. Understanding their structure is key to manipulating these compounds for various applications.

Chemical Nomenclature Basics

Chemical nomenclature is a system of naming chemical compounds so that their chemical makeup is easily understood by chemists worldwide. It's like a universal language in chemistry.

When naming organic compounds, especially hydrocarbons like your examples, several rules are followed:

• The longest continuous chain of carbon atoms is identified; this determines the base name (e.g., "pentene" for 5 carbons).
• Numbering is essential; it starts from the end closest to the double bond, ensuring the double bond or substituents have the lowest possible numbers.
• Substituents, like methyl or ethyl groups, are named and numbered according to their position attached to the main carbon chain.
• Prefixes are added for additional identical substituents, such as "di-" or "tri-" for two or three groups respectively.

These guidelines help in writing and interpreting chemical formulas accurately, allowing for effective communication and comprehension across the field.

Hydrocarbon Compounds Insight

Hydrocarbon compounds are the simplest form of organic compounds, containing only carbon and hydrogen atoms. They are categorized into different classes based on bonding and structure.

In your exercise, we've dealt with alkenes, which are hydrocarbons containing double bonds:

• Alkenes are unsaturated hydrocarbons, denoted by the "-ene" suffix.
• The presence of a double bond adds reactivity, making alkenes important in chemical synthesis.
• Isomerism is common in alkenes, where compounds with the same molecular formula have different structures or spatial arrangements.

Condensed structural formulas are shortened versions of full chemical formulas, highlighting the arrangement of atoms in a molecule. For alkenes, this includes signifying the double bond position and any additional side chains or groups. Understanding the structure and behavior of hydrocarbons is fundamental in organic chemistry, aiding in everything from creating fuels to developing new materials and drugs.