Question

Supply condensed or structural formulas for the following substances. (a) 1,5 -cyclooctadiene (an intermediate in the manufacture of resins) (b) 3,7,11 -trimethyl- 2,6,10 -dodecatriene- 1 -ol (farnesol \(-\) odor of lily of the valley) [Hint: Dodeca means \(12 .]\) (c) 2,6 -dimethyl- 5 -hepten- 1 -al (used in the manufacture of perfume).

Short answer

The condensed or structural formulas for 1,5 -cyclooctadiene, 3,7,11 -trimethyl- 2,6,10 -dodecatriene- 1 -ol and 2,6 -dimethyl- 5 -hepten- 1 -al can be drawn by decoding the IUPAC names and representing chemical connections between atoms as indicated by their positions in the name. The respective compounds should correspond to their names in atom count and structure.

Step-by-step solution

Draw Structure for 1,5 -cyclooctadiene

1,5 -cyclooctadiene is a cycloalkene, a class of compound with one or more carbon rings and one or multiple double bonds. 'Cycloocta' represents an eight-membered carbon ring. 'Diene' indicates there are two double bonds in this molecule, at positions 1 and 5. Hence, draw an eight-membered ring and place double bonds between the 1st-2nd and 5th-6th carbons.

Draw Structure for 3,7,11 -trimethyl- 2,6,10 -dodecatriene- 1 -ol

'Dodeca' indicates a twelve-carbon chain, while 'triene' indicates the presence of three double bonds, located at positions 2, 6, and 10. '3,7,11-trimethyl' signifies the existence of three methyl groups (-CH3), attached at carbon atoms 3, 7, and 11. '1-ol' indicates the presence of a hydroxyl (-OH) group at the 1st carbon atom. To draw the structure, start with a twelve-carbon chain, then add the double bonds, methyl groups, and the hydroxyl group at their respective positions.

Draw Structure for 2,6 -dimethyl- 5 -hepten- 1 -al

'Hepta' indicates a seven-carbon chain. 'ene' means there is one double bond, and it's located at position 5. '2,6-dimethyl' signifies the existence of two methyl groups on the 2nd and 6th carbon atoms. '1-al' signifies an aldehyde functional group (-CHO) at carbon atom 1. Start by drawing a seven-carbon chain and then add the double bond, methyl groups, and the aldehyde group at their respective positions.

Key concepts

Structural Formulas

Structural formulas in organic chemistry depict how atoms are arranged in a molecule. This is different from molecular formulas which only show the type and number of atoms. Structural formulas actually present the connectivity and structure of the molecule, making it easier to understand the physical and chemical properties of the compound. Visualizing the structures can aid in predicting the reactivity patterns of the molecules.

In the case of the exercise, structural formulas help us understand the layout of complex molecules like 1,5-cyclooctadiene or farnesol. They show how elements such as carbon (C), hydrogen (H), and oxygen (O) are connected. Understanding structural formulas is crucial for interpreting chemical behavior.

Typically, bonds between the carbon atoms, as well as additional functional groups such as hydroxyls (–OH) or methyl groups (–CH₃), are shown in these formulas. If you're learning organic chemistry, practice drawing structural formulas to better navigate through more complex compounds.

Cycloalkenes

Cycloalkenes are a fascinating group of hydrocarbons characterized by a ring structure and the inclusion of at least one carbon-carbon double bond. The term 'cyclo' suggests a cyclic or ring structure in the compound, while 'alkene' indicates the presence of a double bond.

In the exercise, 1,5-cyclooctadiene serves as an example. Here, the 'octa' in cyclooctadiene indicates an eight-carbon ring, and 'diene' denotes two double bonds. It's important to note that double bonds influence the chemical reactivity of the compound. In terms of molecular structure, cycloalkenes are viewed as more reactive than cycloalkanes due to the strain in the ring structure caused by the double bonds.

Cycloalkenes are often used in the synthesis of various chemical compounds, including the manufacture of resins, making them essential in industrial chemistry. Understanding their structure helps in predicting how they might interact in reactions, which is valuable in the development of new materials and chemicals.

Molecular Structure

Molecular structure refers to the three-dimensional arrangement of atoms in a molecule. Understanding this concept is fundamental in organic chemistry, as it influences how molecules function in reactions. The shape of a molecule affects properties such as polarity, reactivity, and even biological activity.

In exercises like the one given, constructing the molecular structure involves taking the provided chemical names and arranging the atoms accordingly. For instance, in 3,7,11-trimethyl-2,6,10-dodecatriene-1-ol, the molecular structure is not just a sequence of atoms but a three-dimensional shape that includes branching methyl groups and positioned double bonds.

Visualization tools, like molecular models or software tools, can help better understand this concept by allowing one to "see" the molecule beyond a two-dimensional drawing. Understanding molecular structure aids in deciphering numerous chemical properties and behaviors that can arise due to different atomic arrangements in a compound.

Organic Compounds

Organic compounds are chemical substances that are mainly composed of carbon atoms in combination with hydrogen, nitrogen, oxygen, and other elements. They form the basis of all life on earth and are widely studied because of their complexity and diversity.

The complexity arises due to carbon's unique ability to form stable chains and rings with its atoms. This makes the study of organic compounds essential in fields like biochemistry, pharmaceuticals, and environmental science.

In the exercises like the one presented, compounds such as farnesol and dimethyl heptenal show how varied organic structures can be. These compounds exhibit different functional groups which dictate their use and function, such as the use of 2,6-dimethyl-5-hepten-1-al in perfumes due to its scent. Understanding organic compounds involves exploring these diverse structures and their associated chemical behaviors.