The carbonyl stretch of an amide is typically found around 1,675 wavenumbers; while, the carbonyl stretch of an ester is typically found around 1,725 wavenumbers. Using complete sentences, explain the observed difference in carbonyl stretches for these two functional groups.

Explanation:

In the attached file , the resonance structure of amide and ester has been given . One can find that due to oxygen being more electronegative than nitrogen , the contribution of second resonance structure is more . Hence the double bond character of carbonyl bond ( =C=O ) as double bond is less . It is more in the form of single bond . ( see the resonance structure )

On the other hand it is not so in ester because of absence of nitrogen atom. Here carbonyl group is more in the form of double bond . The stretching wave number for double bond is more because it has greater energy .

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.

alkaline metals are lithium, sodium, rubidium, potassium, cesium and francium.

alkali metals have electronegativity from 0.7 to 1, lowest in periodic table of elements, which means that alkali metals (i group in periodic table) has positive oxidation number in compounds.

electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.

alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons,

for example, potassium is the alkali metal and has a single valence electron in the outer electron shell.

electron configuration of potassium is: ₁₉k 1s²2s²2p⁶3s²3p⁶4s¹.

they can not exist alone in nature, because they are very reactive.