Questions 1 Draw two structural isomers for CsHi00 that woul

Questions 1. Draw two structural isomers for CsHi00 that would both give positive iodoform tests. 2. Carbohydrates with aldehyde groups (aldoses) react with Tollen\'s reagent. Why are they called \"reducing\" sugars? 3. Semicarbazide hydrochloride has two NH2 groups, both have lone pair electrons, yet only one reacts with the carbonyl group in an aldehyde or ketone. With the aid of resonance structures of the semicarbazide, explain why this occurs.

Solution

1) C₅H₁₀O , it two structures give positive iodoform test. they are

CH₃-CO-CH₂-CH₂-CH₃.   CH₃-CO-CH(CH₃)₂

2-pentanone methyl isopropyl ketone.

carbonyl compounds having CH₃-CO- group give positive iodoform test.

2) aldehyde group in carbohydrates react with tollens reagent, then aldehyde reduces the tollens reagent .that why they are called reducings sugars.

tollens reagent(Ag⁺) +-CHO -----------> Ag + -COOH.

3) semicarbazide hydrochloride has two lone pairs on two nitrogen atoms. it react with aldehyde or ketone only one lonepair is involved and the other one is participated in resonance. it shown in below

^-Cl⁺H₃N -^..NH₂-CO-^..NH₂ --------------A----->  ^-Cl⁺H₃N -^..NH₂-CO^-=⁺NH₂

B A   

-----------------B-----> ^-Cl⁺H₃N -N⁺H₂-CO^--^..NH₂