Question

Give the name or condensed structural formula, as appropriate: (a) CCC(C)C(C)(C)C (b) CCCC(C)C(C)CC (c) \(2,5,6\)-trimethylnonane (d) 3-propyl-4,5-dimethylundecane (e) 1-ethyl-3-methylcyclohexane , (d) an alkyne.

Short answer

(a) 2,3,4-trimethylpentane (b) 4-methyl-6-ethylheptane (c) CH_3CH(CH_3)CH_2CH(CH_3)CH(CH_3)CH_2CH_2CH_3 (d) CH_3CH_2CH(C_3H_7)CH(CH_3)CH(CH_3)CH_2CH_2CH_2CH_2CH_3 (e) CH(CH_3)C(C_2H_5)CH_2CH_2CH_2

Step-by-step solution

a) Name for the given SMILES notation: CCC(C)C(C)(C)C

The given SMILES notation represents a molecule composed of carbon and hydrogen atoms. To give the IUPAC name, first check for functional groups, identify the longest carbon chain, and number the carbons. 1. Identify the main chain: - In this case, the longest carbon chain is four carbon atoms long. 2. Number the carbons: - The numbering should be from right to left, starting with the carbon attached to the two methyl groups. 3. Name the substituents: - There are three methyl groups present at positions 2, 3, and 4. 4. Combine the names: - The IUPAC name for the given structure is 2,3,4-trimethylpentane.

b) Name for the given SMILES notation: CCCC(C)C(C)CC

For this SMILES notation, apply the same steps as above. 1. Identify the main chain: - In this case, the longest carbon chain is seven carbon atoms long. 2. Number the carbons: - The numbering should be from left to right, starting with the carbon attached to the two methyl groups. 3. Name the substituents: - There is a methyl group at position 4 and an ethyl group at position 6. 4. Combine the names: - The IUPAC name for the given structure is 4-methyl-6-ethylheptane.

c) Condensed structural formula for 2,5,6-trimethylnonane

To draw the condensed structural formula: 1. Draw the main chain: - A nonane has 9 carbons in a straight chain. 2. Add the substituents: - Place methyl groups at positions 2, 5, and 6. The condensed structural formula for 2,5,6-trimethylnonane is CH_3CH(CH_3)CH_2CH(CH_3)CH(CH_3)CH_2CH_2CH_3.

d) Condensed structural formula for 3-propyl-4,5-dimethylundecane

To draw the condensed structural formula: 1. Draw the main chain: - An undecane has 11 carbons in a straight chain. 2. Add the substituents: - Place a propyl group at position 3 and methyl groups at positions 4 and 5. The condensed structural formula for 3-propyl-4,5-dimethylundecane is CH_3CH_2CH(C_3H_7)CH(CH_3)CH(CH_3)CH_2CH_2CH_2CH_2CH_3.

e) Condensed structural formula for 1-ethyl-3-methylcyclohexane

To draw the condensed structural formula: 1. Draw the cyclohexane ring: - A cyclohexane has 6 carbons in a cyclic structure. 2. Add the substituents: - Place an ethyl group at position 1 and a methyl group at position 3. The condensed structural formula for 1-ethyl-3-methylcyclohexane is CH(CH_3)C(C_2H_5)CH_2CH_2CH_2.

Key concepts

IUPAC Nomenclature

The International Union of Pure and Applied Chemistry (IUPAC) developed a systematic way to name chemical compounds, ensuring consistency and clarity across different languages and regions. In organic chemistry, IUPAC nomenclature is crucial for identifying compounds based on their structure rather than common names, which might vary. This method involves several steps:

• Identifying the longest carbon chain in the compound, which determines the base name (e.g., pentane, hexane).
• Numbering the chain so that substituents (attachments) get the lowest possible numbers.
• Identifying and naming the substituents (such as methyl, ethyl).
• Listing substituents in alphabetical order, using numbers to indicate their positions on the main chain.
• Combining all these parts into one full name, indicating both structure and composition.

This systematic approach helps ensure that the name reflects the compound's molecular structure clearly.

Structural Formula

Structural formulas play a significant role in visualizing the arrangement of atoms within a molecule. Unlike molecular formulas, which only indicate the types and numbers of atoms, structural formulas show the connections between atoms, helping convey the geometry of the molecule.

• Condensed structural formulas simplify this representation by omitting some of the bonds to make it easier to read and write.
• For example, in 2,5,6-trimethylnonane, the condensed structural formula is CH₃CH(CH₃)CH₂CH(CH₃)CH(CH₃)CH₂CH₂CH₃, showing the main chain and methyl group locations without displaying every single bond.
• This helps students conceptualize chemical structures when drawing them out manually, providing a visual learning aid to understand complex molecules.

By practicing structural formulas, students learn to convert a name (from IUPAC) to a structure, aiding both their reading and writing of chemical literature.

SMILES Notation

Simplified Molecular Input Line Entry System (SMILES) provides a way to describe a chemical structure using short ASCII strings, useful in digital databases and computational chemistry. Utilizing SMILES, chemists can denote complex molecules compactly and without the spatial limitations of text.

• Each character or group of characters in a SMILES string represents a part of the molecule or a chemical feature.
• For example, the SMILES string CCC(C)C(C)(C)C corresponds to 2,3,4-trimethylpentane, representing the main carbon backbone and substituents with brackets indicating branches.
• This language allows programs to interpret and transform strings back into chemical structures, facilitating research, data sharing, and education.

SMILES notation is particularly invaluable for chemists designing drugs, as it provides a precise way to store and communicate molecular data.

Alkanes and Alkynes

Alkanes and alkynes are fundamental types of hydrocarbons in organic chemistry. Alkanes are saturated hydrocarbons, meaning they contain only single bonds between carbon atoms. These compounds follow the general formula C\(_n\)H\(2n+2\) and are known for their stable and unreactive nature. Common examples include methane, ethane, and propane.

• Alkanes are often called "paraffins," a term originating from the Latin 'parum' (too little) and 'affinis' (affinity), highlighting their low reactivity.
• They form the backbone of many organic molecules, acting as scaffolds to which functional groups are attached.

On the other hand, alkynes are unsaturated hydrocarbons with at least one carbon-carbon triple bond, following the formula C\(_n\)H\(2n-2\). Acetylene is the simplest alkyne, widely known for its use in welding torches.

• Alkynes are more reactive than alkanes due to the presence of triple bonds that provide sites for chemical reactions.
• This reactivity makes them valuable in synthetic organic chemistry, where they serve as intermediates in the preparation of more complex molecules.

Cycloalkanes

Cycloalkanes are a type of saturated hydrocarbon where the carbon atoms are arranged in a ring or cyclic structure. These are named similarly to alkanes but with the addition of the "cyclo-" prefix to indicate the ring structure.

• The simplest cycloalkane is cyclopropane, a three-membered ring, followed by cyclobutane, cyclopentane, and cyclohexane.
• Unlike straight-chain alkanes, cycloalkanes can have ring strain due to angles that are less than the ideal tetrahedral angle of 109.5°.
• This strain can make them more reactive than their open-chain counterparts.

Substituted cycloalkanes, like 1-ethyl-3-methylcyclohexane, introduce various functional groups to the ring. These groups can affect the cycloalkane's properties, such as its boiling and melting points.
Cycloalkanes form the basis for studying many biochemical and industrial processes and can act as models for understanding the behavior of cyclic structures in larger organic molecules.