Question

Draw both condensed and line structures corresponding to the following IUPAC names: (a) 3-Methylhept-1-ene (b) 4,4 -Dimethylpent-2-yne (c) 2 -Methylhex -3 -ene (d) 1,3,3 -Trimethylcyclohexene

Short answer

Use IUPAC names to draw main chains, place double/triple bonds, and add substituents.

Step-by-step solution

Understanding the IUPAC Name

The IUPAC name provides the necessary information to construct the molecule. Each part of the name indicates a part of the structure: the root part tells us the number of carbon atoms in the longest chain, any substituents describe branches coming off this main chain, and the suffix (e.g., “-ene,” “-yne”) tells us about the type of carbon-carbon bonds.

Constructing Molecule A: 3-Methylhept-1-ene

1. Identify the main chain: 'hept' indicates 7 carbon atoms. 2. Identify the unsaturation: '-1-ene' indicates a double bond between C1 and C2. 3. Locate the substituent: '3-methyl' means a methyl group (CH₃) on C3. 4. Draw the structure: Connect 7 carbon atoms as a chain, place a double bond between C1 and C2, and add the CH₃ group on C3.

Condensed and Line Structures for A

Condensed structure: CH₂=CH-CH(CH₃)-CH₂-CH₂-CH₂-CH₃. Line structure: A line starts from the double bond, progresses through the main chain, with a branch indicated by lines coming off the main fork.

Constructing Molecule B: 4,4-Dimethylpent-2-yne

1. Identify the main chain: 'pent' indicates 5 carbon atoms. 2. Identify the unsaturation: '-2-yne' indicates a triple bond between C2 and C3. 3. Locate the substituents: '4,4-dimethyl' means two methyl groups on C4. 4. Draw the structure: Connect a 5-carbon chain, place a triple bond between C2 and C3, and add two CH₃ groups on C4.

Condensed and Line Structures for B

Condensed structure: CH₃-C≡C-CH(CH₃)₂-CH₃. Line structure: The main chain is drawn with the triple bond between the second and third carbon, with branches at the fourth carbon.

Constructing Molecule C: 2-Methylhex-3-ene

1. Identify the main chain: 'hex' indicates 6 carbon atoms. 2. Identify the unsaturation: '-3-ene' indicates a double bond between C3 and C4. 3. Locate the substituent: '2-methyl' means a methyl group on C2. 4. Draw the structure: Make a 6-carbon chain, place a double bond at C3, and put a CH₃ group on C2.

Condensed and Line Structures for C

Condensed structure: CH₃-CH(CH₃)-CH=CH-CH₂-CH₃. Line structure: The main chain includes the double bond and the methyl group is shown sticking off the second carbon.

Constructing Molecule D: 1,3,3-Trimethylcyclohexene

1. Identify the base structure: 'cyclohexene' indicates a 6-carbon cyclic structure with one double bond. 2. Identify the unsaturation: The double bond is usually between C1 and another carbon. 3. Locate the substituents: '1,3,3-trimethyl' means CH₃ groups are at C1, and two CH₃ groups at C3. 4. Draw the structure: Create a hexagon, place a double bond in it, add methyl groups as specified.

Condensed and Line Structures for D

Condensed structure: (CH₃)₂C=CH-CH₂-CH(CH₃)-CH₂. Line structure: A hexagon with a double bond and methyl group lines coming off.

Key concepts

Condensed Structure

A condensed structure is a simplified way to represent the molecules of organic compounds. It groups the atoms together, typically focusing on how hydrogen atoms are attached to carbon atoms. This format avoids drawing all individual bonds, emphasizing the connectivity in a compact form.

Here's how you can think about it:

• Atoms in the same carbon group are typically shown together, like CH₃ or CH₂, reducing visual clutter.
• The order of groups indicates the order of the atoms along the main chain or structure.

For instance, in the condensed structure of 3-Methylhept-1-ene, it's written as CH₂=CH-CH(CH₃)-CH₂-CH₂-CH₂-CH₃. This vividly shows the arrangement and even hints at the double bond between the first two carbons. Condensed structures are particularly useful in quickly communicating the backbone of a molecule, like a shorthand notation for chemists.

Line Structure

The line structure provides another popular method to depict organic molecules, often used in organic chemistry due to its simplicity. This method uses lines to represent carbon bonds, omitting labels for carbon and hydrogen atoms bonded directly to carbon, while non-carbon atoms and hydrogen only attached to non-carbon atoms need to be visible.

Key points include:

• A vertex or the end of a line represents a carbon atom.
• Lines connecting these indicate bonds between carbons.

If we consider the line structure of 3-Methylhept-1-ene, it would appear as a zigzag line, mirroring the main carbon chain, with add-ons for branches, like the methyl group on the third carbon. The initial double bond is displayed as a double line, offering insights into the unsaturation in the molecule. Overall, line structures provide a clear view of a molecule's skeleton, perfect for visualizing complex structures.

IUPAC Naming

IUPAC naming, or International Union of Pure and Applied Chemistry naming, provides a standardized way to name chemical substances, including complex organic molecules. The names convey a significant amount of detail about the structure and functional groups of the molecule, letting chemists understand its composition and framework at a glance.

The entire name consists of root, prefix, infix, and suffix:

• The root indicates the longest carbon chain or the main cyclic structure.
• The prefix indicates the presence of side chains or additional groups.
• The infix or suffix points out the presence of double or triple bonds, like "-ene" for double bonds and "-yne" for triple bonds.

By using the IUPAC system, one can derive the formula of the compound meticulously by decomposing the name, like interpreting 3-Methylhept-1-ene, which tells us about a 7-carbon chain (hept), a double bond starting at the first carbon, and a methyl group at the third carbon. This universal system ensures clarity and precision in chemical communication.

Organic Molecule Construction

The task of organic molecule construction begins with comprehending the detailed information provided by IUPAC names. This name-driven approach helps chemists visualize and build molecular structures effectively.

Critical steps include:

• Identifying the main carbon backbone from the root word in the name.
• Pinpointing the location and type of multiple bonds as defined by the suffix.
• Adding substituent groups or branches at the specified carbon locations.

For example, to construct 3-Methylhept-1-ene, one starts with drawing a 7-carbon chain (hept). Then, introduce a double bond between the first and second carbons (1-ene), and finally add a methyl group on the third carbon (3-methyl). This stepwise construction facilitates a systematic and clear approach to constructing any given molecule from its IUPAC name, ensuring each atom and bond is correctly placed according to the description.