Question

Draw structural formulas for the following compounds. (a) 3-Iodo-1-propene (b) \((R)-2\)-Chlorobutane (c) meso-2,3-Dibromobutane (d) trans-1-Bromo-3-isopropylcyclohexane (e) 1 -Iodo-2,2-dimethylpropane (f) Bromocyclobutane

Short answer

Answer: The structural formulas for each compound are as follows: 3-Iodo-1-propene: H2C=CH-CH2-I (R)-2-Chlorobutane: H | CH3-CH-CH2-CH3 | Cl meso-2,3-Dibromobutane: Br Br | | CH3-CH-CH-CH3 | | H H trans-1-Bromo-3-isopropylcyclohexane: Br | C----C---CH(CH3)2 / \ C C |\ |\ | C--------C | \| |/ C---------C 1-Iodo-2,2-dimethylpropane: I-CH2-C(CH3)2 Bromocyclobutane: Br | C / \ C----C |\ |\ | C--C| \| |/ C--C

Step-by-step solution

Identify main chain and functional groups

To draw the structural formula for each compound, we need to identify the primary chain and any functional groups. This can be done by analyzing the name of the compound, breaking it down into the different components, and identifying the connectivity of different atoms. The IUPAC nomenclature system will help us in this process.

Draw 3-Iodo-1-propene

The name 3-Iodo-1-propene tells us that the primary chain is propene, which is a three-carbon alkene. The "1" before "propene" means that the double bond is between the first and the second carbon atoms. The "3-Iodo" tells us that there is an iodine atom on the third carbon atom. Based on this information, we can draw the structure: H2C=CH-CH2-I

Draw (R)-2-Chlorobutane

The name (R)-2-Chlorobutane tells us that the primary chain is butane (4-carbon alkane), and a chlorine atom is on the second carbon atom. The (R) denotes the absolute configuration of the stereocenter (the chiral carbon atom), which means that the structure has the R-configuration at the second carbon atom. Based on this information, we can draw the structure: H | CH3-CH-CH2-CH3 | Cl

Draw meso-2,3-Dibromobutane

The name meso-2,3-Dibromobutane tells us that the primary chain is butane, and there are two bromine atoms, one on the second carbon atom and another on the third carbon atom. The "meso" denotes that the compound has a plane of symmetry, meaning the two chiral carbon atoms have opposite configurations. Based on this information, we can draw the structure: Br Br | | CH3-CH-CH-CH3 | | H H

Draw trans-1-Bromo-3-isopropylcyclohexane

The name trans-1-Bromo-3-isopropylcyclohexane tells us that the primary ring is cyclohexane, a bromine atom is on the first carbon atom, and there is an isopropyl group on the third carbon atom. The "trans" denotes that these two substituents are on opposite sides of the cyclohexane ring. Based on this information, we can draw the structure: Br | C----C---CH(CH3)2 / \ C C |\ |\ | C--------C | \| |/ C---------C

Draw 1 -Iodo-2,2-dimethylpropane

The name 1-Iodo-2,2-dimethylpropane tells us that the primary chain is propane, an iodine atom is on the first carbon atom, and there are two methyl groups on the second carbon atom. Based on this information, we can draw the structure: I-CH2-C(CH3)2

Draw Bromocyclobutane

The name Bromocyclobutane tells us that the primary ring is cyclobutane and there is a bromine atom attached to one of the carbon atoms. Based on this information, we can draw the structure: Br | C / \ C----C |\ |\ | C--C| \| |/ C--C

Key concepts

IUPAC Nomenclature

In organic chemistry, IUPAC nomenclature is a method of naming organic chemical compounds as recommended by the International Union of Pure and Applied Chemistry (IUPAC). Having a standardized naming convention ensures that every compound has a unique and unambiguous name. When we decipher a compound's name, like '3-Iodo-1-propene', we break it down into parts: the prefix '3-Iodo' indicates an iodine on the third carbon, and '1-propene' tells us there's a double bond starting at the first carbon of a three-carbon chain. In '(R)-2-Chlorobutane', the '(R)' indicates the absolute configuration at a chiral center, specifying the spatial arrangement of the substituents.

To correctly draw the structure from such names, here are a few steps to follow:

• Identify the longest carbon chain as the base name.
• Determine the position of functional groups and double or triple bonds from the numbers in the name.
• For chiral centers, use the (R)/(S) configuration to orient the groups correctly.
• Compile everything together to represent the molecular structure.

This process is crucial, as the structure of a molecule is directly tied to its function and properties.

Stereochemistry

Stereochemistry involves the study of the spatial arrangements of atoms in molecules and the impact of this arrangement on their chemical behavior. The example of '(R)-2-Chlorobutane' showcases a molecule with a single chiral center, where (R) denotes the arrangement following a set of priority rules. Meso compounds, like 'meso-2,3-Dibromobutane', have multiple chiral centers but are superimposable on their mirror image due to a plane of symmetry. This character gives them unique properties such as being optically inactive despite having chiral centers.

Here are key points when considering stereochemistry in structural formulas:

• Determine the configuration (R or S) of chiral centers.
• Evaluate if the molecule is chiral or achiral, considering symmetry.
• In cases of di-substituted cycloalkanes, like 'trans-1-Bromo-3-isopropylcyclohexane', the 'trans' or 'cis' notation determines the relative positions of substituents around the ring.

Understanding stereochemistry is fundamental for predicting the reactions and interactions of molecules, particularly in areas like pharmaceuticals where the correct stereochemistry can mean the difference between a useful drug and an ineffective or harmful one.

Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. They play a vital role in determining the properties of organic compounds. For instance, the '1-Iodo-2,2-dimethylpropane' compound includes an iodo group attached to the end carbon. Functional groups are like the 'active site' of the molecule and typically involve heteroatoms like oxygen, nitrogen, sulfur, or halogens like chlorine and bromine. The 'Bromocyclobutane' compound, for example, includes a bromine atom attached to a cyclobutane ring.

To recognize functional groups in a compound name, look for these indicators:

• Prefixes or suffixes like 'ol' for alcohols, 'al' for aldehydes, or 'amine' for amines.
• Halogen naming like 'bromo', 'chloro', or 'iodo' which indicates the presence of a halogen atom.
• The position of the functional group denoted by a number on the carbon chain.

Identifying functional groups is crucial for understanding the reactivity and interactions of organic molecules, and is a foundational concept in organic chemistry studies.