Question

Write structural formulas corresponding to these condensed formulas. (a) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{CCH}_{2} \mathrm{CH}\left(\mathrm{CH}_{3}\right) \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}\) (b) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHCH}_{2} \mathrm{C}\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CH}_{2} \mathrm{Br}\) (c) \(\mathrm{Cl}_{3} \mathrm{CCH}_{2} \mathrm{CH}\left(\mathrm{CH}_{3}\right) \mathrm{CH}_{2} \mathrm{Cl}\).

Short answer

The structural formulas corresponding to the given condensed formulas are: (a) every carbon atom is attached to at least one other carbon, except the ends which are capped with a CH3 group, (b) the central carbon atom is attached to a CH2 group, a CH3 group, and a bromine atom, and (c) there are two carbon single bonded to chlorine atoms (one bonded to three chlorines and one bonded to a single chlorine).

Step-by-step solution

Interpreting Condensed Formulas (a)

The condensed formula can be broken down into individual parts: \((\mathrm{CH}_{3})_{3}\) \(\mathrm{CCH}_{2}\) \(\mathrm{CH}\left(\mathrm{CH}_{3}\right)\) \(\mathrm{CH}_{2}\) \(\mathrm{CH}_{2}\) \(\mathrm{CH}_{3}\). Drawing this out structurally, we start with a carbon that has 3 hydrogen atoms attached, followed by a carbon with 2 hydrogens, another carbon with a CH3 group, and carbons each with two hydrogen, ending with a carbon with 3 hydrogen atoms.

Interpreting Condensed Formulas (b)

\(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHCH}_{2}\mathrm{C}\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CH}_{2} \mathrm{Br}\) starts out with a carbon with two hydrogen atoms, followed by another carbon with two hydrogens, a carbon with 2 CH3 group and ends with a carbon with a hydrogen and a bromine atom.

Interpreting Condensed Formulas (c)

\(\mathrm{Cl}_{3} \mathrm{CCH}_{2} \mathrm{CH}\left(\mathrm{CH}_{3}\right)\mathrm{CH}_{2} \mathrm{Cl}\) starts with a carbon with three chlorine atoms, followed by a carbon with two hydrogens, a carbon with a CH3 group, then a carbon with two hydrogens and ends with a carbon with a chlorine atom.

Key concepts

Condensed Formulas

In organic chemistry, condensed formulas are a way of writing the structure of molecules that conveys information about the types and sequences of atoms without showing each bond explicitly. They provide a streamlined method of expressing a molecule's composition and connectivity between its atoms, which can be elaborated into a more complex structural formula.

For example, the condensed formula for a molecule could look like \(\left(\mathrm{CH}_{3}\right)_{3}\mathrm{CCH}_{2}\mathrm{CH}\left(\mathrm{CH}_{3}\right)\mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{CH}_{3}\), where the parentheses and subscripts indicate groups of atoms and how many times they repeat in the molecule. In this case, it denotes a carbon chain with various CH3 (methyl) groups attached. Such a notation is immensely helpful in organic chemistry as it simplifies the representation of complex molecules, making it easier to grasp their structure at a glance without drawing every single bond.

Hydrocarbon Structures

Hydrocarbons are fundamental to the study of organic chemistry and consist of molecules made up of hydrogen and carbon atoms only. The structures of hydrocarbons can range from simple straight chains to complex branched chains and rings.

Two primary types of hydrocarbons are alkanes, with single bonds, and alkenes with one or more double bonds. The chain length, the presence of side chains (alkyl groups), and branching all affect the molecular formula of a hydrocarbon. For instance, \(\left(\mathrm{CH}_{3}\right)_{2}\mathrm{CHCH}_{2}\mathrm{C}\left(\mathrm{CH}_{3}\right)_{2}\mathrm{CH}_{2}\mathrm{Br}\) suggests a branched hydrocarbon with a bromine substituent. Recognizing the patterns in which carbon chains are assembled and the corresponding names is crucial for mastering organic chemistry.

Organic Compound Nomenclature

Nomenclature in organic chemistry is a systematic method of naming organic chemical compounds as recommended by the International Union of Pure and Applied Chemistry (IUPAC). The rules of nomenclature are designed to give each compound a unique and unambiguous name, and also to imply the structure of the compound.

Naming an organic compound involves identifying the length of the carbon chain, the presence and position of any functional groups, and the location of any branches or substitutions. A molecule like \(\mathrm{Cl}_{3}\mathrm{CCH}_{2}\mathrm{CH}\left(\mathrm{CH}_{3}\right)\mathrm{CH}_{2}\mathrm{Cl}\) would require using prefixes and suffixes to indicate the number of chlorines (trichloro), the presence of a methyl group (methane derivative), and other structural details in its name.

Representing Chemical Structures

Representing chemical structures accurately is crucial for understanding reactivity, properties, and the spatial arrangement of molecules. Beyond condensed formulas, organic chemists use multiple types of formulas to depict molecules, including the structural formula, skeletal formula, and molecular formula.

Each type serves a specific purpose; for example, the structural formula shows the molecule in two dimensions with all atoms and bonds represented, while the skeletal formula abstracts away the hydrogen atoms attached to carbons, allowing for more straightforward visualization of complex molecules. The molecular formula, on the other hand, provides only the number of different atoms in a molecule. Learning how to convert between these representations is an essential skill, helping students to visualize and understand molecular shapes and potential reactions.