Question

\- Draw structures corresponding to the following IUPAC names: (a) 2,3 -Dichloro-4-methylhexane (b) 4 -Bromo-4-ethyl-2-methylhexane (c) 3 -Iodo- \(2,2,4,4\) -tetramethylpentane (d) cis-1-Bromo-2-ethylcyclopentane

Short answer

Draw structures by identifying carbon chains, numbering them, and adding substituents in given positions with correct spatial arrangements.

Step-by-step solution

Understanding IUPAC nomenclature

Start by identifying the main chain in each IUPAC name. The main chain is the longest continuous chain of carbon atoms. Identify the parent hydrocarbon, and recognize that the substituents are prefixed before the main chain.

Drawing 2,3-Dichloro-4-methylhexane

The parent chain is 'hexane,' indicating a 6-carbon chain. Number from one end to ensure substituents are on low numbers. Position chlorine on the second and third carbons and a methyl group on the fourth carbon. Draw the carbon skeleton and add substituents accordingly.

Visualizing 2,3-Dichloro-4-methylhexane

The skeletal structure looks like this: Cl- ext{C}- ext{C}(Cl)- ext{C}(CH₃)- ext{C}- ext{C}- ext{C} with each carbon connected appropriately to match a hexane chain.

Drawing 4-Bromo-4-ethyl-2-methylhexane

The main chain here is also 'hexane.' Start numbering to keep substituents' positions minimal: at position 4, add both a bromine atom and an ethyl group, and at position 2, add a methyl group. Draw out this structure.

Visualizing 4-Bromo-4-ethyl-2-methylhexane

The skeletal representation: Br-( ext{C}- ext{C})-CH(CH₂CH₃)- ext{C}(CH₃)- ext{C}- ext{C}. Ensure the correct positioning of bromine, ethyl, and methyl groups on the hexane backbone.

Drawing 3-Iodo-(2,2,4,4)-tetramethylpentane

The main chain is 'pentane.' At position 3, place an iodine atom. Both positions 2 and 4 carry two methyl groups each. This indicates tertiary carbon atoms at these positions with additional methyls.

Visualizing 3-Iodo-(2,2,4,4)-tetramethylpentane

Create a pentane base and insert the iodine at C3 and four methyl groups, two each at C2 and C4. ( ext{C}(CH₃)={(CH₃)}- ext{C}-I- ext{C}(CH₃)={(CH₃)}- ext{C}).

Drawing cis-1-Bromo-2-ethylcyclopentane

The base structure is 'cyclopentane,' a five-membered ring. Position Br and an ethyl group on carbons 1 and 2, respectively. Ensure they reside on the same side since it is 'cis'.

Visualizing cis-1-Bromo-2-ethylcyclopentane

Consider the ring with one group projecting up or down in the same direction. For instance, Br and CH₂CH₃ both project above the plane of the cyclopentane.

Key concepts

Structural Isomers

Structural isomers are fascinating in the world of organic chemistry. They have the same molecular formula but differ in the connectivity of their atoms. Because of their unique structure, they can exhibit different chemical and physical properties.
For example, in the exercise above, each organic compound represents distinct structural arrangements. Despite sharing molecular similarities such as a \(C_6H_{14}Cl_2\) formula for 2,3-Dichloro-4-methylhexane and a \(C_8H_{15}Br\) formula for 4-Bromo-4-ethyl-2-methylhexane, their isomeric nature results from differing placements and types of substituents.
This highlights the significance of precise atom positioning within the structure. Charting out these isomers involves recognizing the main carbon chain and judiciously placing substituents like chlorine, methyl groups, bromine, or ethyl groups. This variation imparts different reactivity and interaction characteristics to each compound.

Organic Chemical Structure Drawing

Drawing organic chemical structures can be as simple as connecting dots in elementary school, yet it demands accuracy. A good practice is to start by identifying the main frame, or the longest continuous carbon chain of the molecule. Then, carefully position substituents, as stated in the IUPAC name, toward creating an accurate structural representation.
For instance, when tackling structures like 3-Iodo- (2,2,4,4)-tetramethylpentane, begin with a pentane base. Pay special attention to ensuring the iodine atom is placed on the third carbon atom. Further, add the four methyl groups on the specified 2nd and 4th carbon atoms, noting that each carbon gets two methyl groups.
Visual representation can involve writing out these as skeletal structures for clarity. Oftentimes, skeletal formulas omit hydrogen atoms, focusing on layout. This enables one to easily see the skeletal connections and positions of substituents relative to the longer carbon chain.

Substituents Positioning

The positioning of substituents is a precise task crucial in defining an organic compound's identity. The key is to assign carbon numbers progressively from one end such that substituents get the lowest possible numbers, adhering to IUPAC's rules.
Take the exercise's example of 2,3-Dichloro-4-methylhexane: numbering must ensure that both chlorine atoms appear on the 2nd and 3rd carbon atoms of the hexane backbone. This ordering minimizes the numerical designations.
In the case of cyclic compounds like cis-1-Bromo-2-ethylcyclopentane, not only is positioning crucial, but so is orientation. For 'cis' configurations, both substituents—bromine and the ethyl group—need to be on the same side of the cyclopentane ring, either both projecting above or below the hypothetical plane of the ring.

• Number after identifying the main chain or ring.
• Ensure the lowest number assignment to substituents.
• Use descriptors like 'cis' or 'trans' for stereochemistry, indicating relative positions.

Remember, these intricacies are what make organic chemistry both challenging and rewarding.