Amide Lewis Structures

Lewis dot formulas are the major means by which structural information is communicated in organic chemistry. These structural formulas show the atoms, bonds, location of unshared pairs, and formal charges. 

Two or more Lewis structures, differing only in the placement of electrons, can often be written for a single compound. In such cases the separate Lewis structures are said to be in resonance, and the true electron distribution is a hybrid of the electron distributions of the contributing structures. 

The amide function is an important structural unit in peptides and proteins. Formamide, represented by the Lewis structure shown, is the simplest amide. It is a planar molecule with a dipole moment of 3.7 D. Lewis structures I-IV represent species that bear some relationship to the Lewis structure for formamide. 

75 Which Lewis formula is a resonance contributor to the structure of formamide  

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Descriptive Passage and Interpretive Problems 1 Amide Lewis Structures... 

Dicyclohexylcarbodiimide is a solid material, the Lewis structure for which resembles that of ketene. The molecule is a widely used catalyst for amide synthesis and other dehydration reactions. 

Given a Lewis structure, a condensed formula, or a line drawing for an organic compound, identify it as representing an alkane, alkene, alkyne, arene (aromatic), alcohol, carboxylic acid, ether, aldehyde, ketone, ester, amine, or amide. 

Draw a Lewis structure for an isomer of C2H5NO that is an amide, and draw a second Lewis structure for a second isomer of C2H5NO that has both an amine functional group and an aldehyde functional group. 

The amide ion, NH2, is a Bronsted base. Represent the reaction between the amide ion and water in terms of Lewis structures. 

Acyl chlorides have C=0 stretching absorptions at higher wavenumber (1800 cm ) than esters, and amides have C=0 stretching absorptions at lower wavenumber (1650—1655 cm ). These different values reflect the contribution of inductive and resonance effects in the stabilization of the Lewis structure of a carbonyl group compared to the dipolar resonance form. The chlorine atom of acyl chlorides inductively withdraws electrons from the carbonyl carbon and destabilizes the dipolar resonance form, thus leading to an increase in the double bond character of the carbonyl group. Figure 21.5 shows the infrared spectrum of acetyl chloride. 

Both nitramide and hyponitrous acid have the formula H2N2O2. Hyponitrous acid is a weak diprotic acid nitramide contains the amide group (—NHg). Draw plausible Lewis structures for these two substances. 

In accordance with the electropositive nature of the bridgehead atoms, all di(pyridyl) substituted anions behave like amides with the electron density accumulated at the ring nitrogen atoms rather than carbanions, phosphides or arsenides. The divalent bridging atoms (N, P, As) in the related complexes should in principle be able to coordinate either one or even two further Lewis acidic metals to form heterobimetallic derivatives. According to the mesomeric structures, (Scheme 7), it can act as a 2e- or even a 4e-donor. However, theoretical calculations, supported by experiments, have shown that while in the amides (E = N) the amido nitrogen does function as... 

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