Bond-line formulas drawing

The dimerization of cyclopentadiene occurs primarily through an endo transition state, as is typical for Diels-Alder reactions, (a) In the reactants, draw red and blue shaded lobes for the orbitals that have favorable secondary interactions in the diene and dienophile, causing the preference for an endo transition state, (b) Using bond-line formulas, draw curved arrows to show the flow of electrons that leads to product formation, and draw a three-dimensional formula for the product, (c) The reaction produces a racemic mixture. Show how the reactants align in three dimensions to form each enantiomer. 

The structural language of organic chemistry has been developed so that complex molecules can be described in a clear, yet economical way. A molecule as complex as cholesterol can be drawn rapidly in a bond-line formula, while drawing even a condensed formula would require a prohibitive amount of time. 

Section 1.9 Condensed formulas and bond-line formulas (skeletal diagrams) are used to economize the drawing of organic structures. 

The most common type of structural formula used by organic chemists, and the fastest to draw, is the bond-line formula. (Some chemists call these skeletal formulas.) The formula in Fig. 1.3 is a bond-line formula for propyl alcohol. The sooner you master the use of bond-line formulas, the more quickly you will be able to draw molecules when you take notes and work problems. And, lacking all of the symbols that are explicitly shown in dash and condensed structural formulas, bond-line formulas allow you to more quickly interpret molecular connectivity and compare one molecular formula with another. 

We apply the following rules when we draw bond-line formulas ... 

Bond-line formulas are easy to draw for molecules with multiple bonds and for cyclic molecules, as well. The following are some examples. 

Open computer molecular models for dimethyl ether, dimethylacetylene, and OT-l,2-dichloro-l,2-difluoroethene from the 3D Molecular Models section of the book s website. By interpreting the computer molecular model for each one, draw (a) a dash formula, (b) a bond-line formula, and (c) a three-dimensional dashed-wedge formula. Draw the models in whatever perspective is most convenient—generally the perspective in which the most atoms in the chain of a molecule can be in the plane of the paper. 

Draw bond-line formulas for all of the isomers of CaHia that have (a) methyl substitu- PRACTICE PROBLEM 4.4 ents, and (b) ethyl substituents. 

Draw bond-line formulas and give lUPAC substitutive names for all of the isomeric alcohols with the formulas (a) C4H 10O and (b) CsHi O. 

STRATEGY AND ANSWER C2 and C4 are chirality centers in 2-bromO 4-chloropentane. We begin by drawing the carbon chain with as many carbons depicted in the plane of the paper as possible, and in a way that maximizes the symmetry between C2 and C4. In this case, an ordinary zig-zag bond-line formula provides symmetry between C2 and C4. Then we add the bromine and chlorine atoms at 02 and 04, respectively, as well as the hydrogen atoms at these carbons, resulting in formula I. To draw its enantiomer (II), we imagine a mirror and draw a reflection of the molecule. 

How To Write and Interpret Structural Formulas 15 How To Draw Bond-Line Formulas 18 1.8A The Use of Curved Arrows How To Write Resonance Structures 24... 

The efficiencies of drawing bond-line formulas come from the fact that no Cs are written for carbon atoms, and generally no Hs are shown for hydrogen atoms, unless they are needed to give a three-dimensional perspective to the molecule (and in that case we use solid or dashed wedges for bonds to the out-of-plane atoms, as described in the following section). Instead, in bond-line formulas ordinary lines represent bonds, and carbon atoms are inferred at each bend in the line and at the ends of lines. 

Yon should be able to draw chemical formulas that show all of the valence electrons in a molecule (Lewis structures), using lines for bonds and dots to show unshared electrons. You should be proficient in representing structures as dash structural formulas, condensed structural formulas, and bond-line structural formulas. In particular, the more quickly you become skilled at using and interpreting bond-line formulas, the faster you will be able to process structural information in organic chemistry. You have also learned about resonance structures, the use of which will help us in understanding a variety of concepts in later chapters. 

The following are two three-dimensional bond-line formulas for 2,3-dibromopentane. Notice that in drawing these formulas we have followed the conventions above. 

Draw condensed and bond-line formulas for each C4H10 isomer. 

Condensed and bond-line formulas are abbreviated representations of molecules. Hashed-wedged line drawings illustrate molecular structures in three dimensions. 

Construct as many constitutional isomers of each molecular formula as you can for (a) C5H12 (b) C3HgO. Draw both condensed and bond-line formulas for each isomer. 

Draw bond-line structures for all constitutional isomers with molecular formula C4H9CI. 

There are five constitutional isomers with molecular formula C6H14. Draw a bond-line structure for each isomer and identify the parent in each case. 

The structural formula shows all of the carbon and hydrogen atoms in the molecnle and how they are bonded together. The condensed structural formula gronps the hydrogen atoms with the carbon atom to which they are bonded. Condensed stractuial foimnlas may show some of the bonds (as the previous examples do) or none at aU. The condensed structural formula for butane can also be written as CH3CH2CH2CH3. The carbon skeleton formula (also called a line formula) shows the carbon-carbon bonds only as lines. Each end or bend of a line represents a carbon atom bonded to as many hydrogen atoms as necessary to form a total of four bonds. Carbon skeleton formnlas allow us to draw complex structures quickly. 

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