Condensation structures

Organic chemists have devised a number of shortcuts to speed the writing of structural formulas Sometimes we leave out unshared electron pairs but only when we are sure enough m our ability to count electrons to know when they are present and when they re not We ve already mentioned representing covalent bonds by dashes In condensed structural formulas we leave out some many or all of the covalent bonds and use sub scripts to indicate the number of identical groups attached to a particular atom These successive levels of simplification are illustrated as shown for isopropyl alcohol ( rub bmg alcohol )... 

An n alkane of molecular formula C28H58 has been isolated from a certain fossil plant Write a condensed structural formula for this alkane J... 

The molecular formula is CnH24 the condensed structural formula is CH3(CH2)9CH3... 

Condensed structural formula (Section 1 7) A standard way of representing structural formulas in which subscripts are used to indicate replicated atoms or groups as in (CH3)2CHCH2CH3... 

Notice that the horizontal bonds between carbons aren t shown in condensed structures—the CH3, CH2, ancl CH units are simply placed next to each other—but the vertical carbon-carbon bond in the first of the condensed structures drawn above is shown for clarity. Notice also in the second of the condensed structures that the two CH3 units attached to the CH carbon are grouped together as (0-13)2. 

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. 

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. 

Condensed structure (Section 1.12) A shorthand way of writing structures in which carbon-hydrogen and carbon-carbon bonds are understood rather than shown explicitly. Propane, for example, has the condensed structure CH3CH2CH3. 

Concanavalin A, secondary structure of. 1038-1039 Concerted reaction, 1178 Condensation reaction, 882 Condensed structure, 22 Cone cells, vision and, 504-505 Configuration. 297... 

Write the condensed structural formulas and molecular formulas for the following molecules. The reactive groups are shown in red. 

Hydrogen bonds can exist in many molecules other than HF, H20, and NH3. The basic requirement is simply that hydrogen be bonded to a fluorine, oxygen, or nitrogen atom with at least one unshared pair. Consider, for example, the two compounds whose condensed structural formulas are... 

To save space we often write condensed structural formulas such as... 

Sfi.f-Tfst 18.IB Write (a) the structural formula of carvonc (11) and (b) the condensed structural formula for... 

Self-Test 18.3A (a) Name the alkene (CH3),CHCH=CH2 and (b) write the condensed structural formula for 2-methylpropene. 

Self-Test 18.4A Write the condensed structural formulas for the five isomeric alkanes of molecular formula C6H14. 

Self-Test 18.8A Write the condensed structural formula of the product of the addition of hydrogen to 2-butene CH3CH=CHCH3 + H2 — product. 

Write the shortened (condensed) structural formula of (a) 3-methyl-l-penrene (b) 4-cth yl-3,3-dimethyl heptane ... 

I Self-Test 19.1 A (a) Write the condensed structural formula of the ester formed from the reaction between propanoic acid, CH3CFI2COOH, and methanol, CH3OH. 

Write the condensed structural formulas of the acid and alcohol that react to form methyl butanoate, CH3(CH2)2COOCH3, a contributor to the flavor of apples. 

Write the condensed structural formulas of the principal products of the reaction that takes place when (a) ethylene glycol, 1,2-ethanediol, is heated with stearic acid, CH,(CH2)i6COOH (b) ethanol is heated with oxalic acid, HOOCCOOH (c) 1-butanol is heated with propanoic acid. 

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