Structure, condensed skeletal

ThomsonNOW Click Organic Interactive to learn how to interconvert skeletal structures, condensed structures, and molecular models. 

Organic molecules are usually drawn using either condensed structures or skeletal structures. In condensed structures, carbon-carbon and carbon-hydrogen bonds aren t shown. In skeletal structures, only the bonds and not the atoms are shown. A carbon atom is assumed to be at the ends and at the junctions of lines (bonds), and the correct number of hydrogens is menially supplied. 

Straight-chain alkane, 80 Strecker synthesis, 972 Structure, condensed, 22 electron-dot, 9 Kekule, 9 Lewis, 9 line-bond, 9 skeletal, 23... 

Using Line Structures, Condensed Structures, and Skeletal Structures... 

Drawing organic molecules presents a special challenge. Because they often contain many atoms, we need shorthand methods to simplify their structures. The two main types of shorthand representations used for organic compounds are condensed structures and skeletal structures. 

As you can see in Figure 22-6, cyclic hydrocarbons such as cyclohexane are represented by condensed, skeletal, and line structures. Line structures show only the carbon-carbon bonds with carbon atoms understood to be at each vertex of the structure. Hydrogen atoms are assumed to occupy the remaining bonding positions unless substituents are present. 

Convert the following condensed structures into skeletal structures (remember that condensed structures show atoms but few, if any, bonds, whereas skeletal stmctures show bonds but few, if any, atoms) ... 

Convert the following condensed structures into skeletal structures ... 

Draw the condensed structural and skeletal formula for each of the following (6.7)... 

Draw the condensed structural and skeletal formula for octane. 

The name of a cycloalkane reveals the number of carbon atoms in the ring. For example, cyclopropane (CjHg) is the smallest cycloalkane, with three carbon atoms in the ring. Cyclobutane (C4Hg) has a ring with four carbon atoms. A cyclic hydrocarbon can be represented by condensed, skeletal, and line structures. These structures are illustrated below for cyclobutane. Chemists usually use line structures to depict cycloalkanes. 

Even simpler than condensed structures is the use of skeletal structures such as those shown in Table 1.3. The rules for drawing skeletal structures are straightforward. 

The general features of this elegant and efficient synthesis are illustrated, in retrosynthetic format, in Scheme 4. Asteltoxin s structure presents several options for retrosynthetic simplification. Disassembly of asteltoxin in the manner illustrated in Scheme 4 furnishes intermediates 2-4. In the synthetic direction, attack on the aldehyde carbonyl in 2 by anion 3 (or its synthetic equivalent) would be expected to afford a secondary alcohol. After acid-catalyzed skeletal reorganization, the aldehydic function that terminates the doubly unsaturated side chain could then serve as the electrophile for an intermolecular aldol condensation with a-pyrone 4. Subsequent dehydration of the aldol adduct would then afford asteltoxin (1). 

The structure of dimer XI (X, where n = 2), obtained by x-ray single crystal analysis (Figure 1), shows that the desired skeletal stabilization based upon 1,4- condensation units has been achieved. 

Knowledge of the chemical structures of the major vitamins was acquired during the 30 years after 1920, and some were identified as known compounds. They were classified as fat-soluble and water-soluble vitamins. The only heterocyclic compounds in the former class are the tocopherols (vitamin E). They were discovered through their action in preventing sterility in rats, but they appear to play an important part in the metabolism of skeletal muscle. Vitamin E deficiency appears to occur rarely in man, but vitamin E therapy is tried in a number of clinical disorders. The tocopherols may be isolated from vegetable oils, and synthetic a-tocopherol (61) is made by condensing trimethylhydroquinone with phytol or phytyl halides (Scheme 2). For medicinal use they may be converted into their acetates or succinates. 

---