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B.Sc Biochemistry Named Reactions — practice questions — page 2

Explore 46 free Named Reactions questions in B.Sc Biochemistry Chemistry. Open each question or exercise to read its content, reference answers and available explanation.

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Named Reactions questions and exercises with answers

Showing questions 31–46 of 46.

**Gatterman–Koch reaction** formylates benzene usingRead the answer and worked solution →**Clemmensen reduction** converts $>C=O$ to $>CH_2$ usingRead the answer and worked solution →**Wolff–Kishner reduction** uses which reagent to convert $>C=O$ to $>CH_2$?Read the answer and worked solution →The **Hell–Volhard–Zelinsky (HVZ) reaction** converts a carboxylic acid (with $\alpha$-H) to an $\alpha$-halo acid usingRead the answer and worked solution →**Hoffmann ammonolysis** of alkyl halide with excess $NH_3$ in sealed tube primarily givesRead the answer and worked solution →**Diazotisation** of a primary aromatic amine uses $NaNO_2 + HCl$ atRead the answer and worked solution →**Sandmeyer's reaction** converts $ArN_2^+X^-$ to $ArCl$ usingRead the answer and worked solution →Sandmeyer's reaction proceeds via which type of intermediate?Read the answer and worked solution →The **Gattermann reaction** (not Gatterman–Koch) converts $ArN_2^+X^-$ to $ArX$ usingRead the answer and worked solution →The **Balz–Schiemann reaction** converts $ArN_2^+$ to $ArF$ via which intermediate?Read the answer and worked solution →Which of the following named reactions does **NOT** require an $\alpha$-hydrogen on the substrate?Read the answer and worked solution →Identify the correct conversion: $CH_3CN \xrightarrow{?} CH_3CHO$ (one step).Read the answer and worked solution →Match each named reaction to its jobRead the answer and worked solution →Match each named reactionRead the answer and worked solution →Which reaction is being described?Read the answer and worked solution →Which one does NOT belong?Read the answer and worked solution →

Worked practice questions

**Gatterman–Koch reaction** formylates benzene using

  1. $RCOCl$ with $AlCl_3$
  2. $CHCl_3$ with aq. $NaOH$
  3. $CO + HCl$ with $AlCl_3$/$CuCl$
  4. $HCHO$ with conc. $H_2SO_4$
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Correct answer: C. $CO + HCl$ with $AlCl_3$/$CuCl$

$C_6H_6 + CO + HCl \xrightarrow{AlCl_3, CuCl} C_6H_5CHO$. Equivalent to a Friedel–Crafts acylation with the in-situ generated formyl cation $HC≡O^+$.

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**Clemmensen reduction** converts $>C=O$ to $>CH_2$ using

  1. $LiAlH_4$
  2. $NH_2NH_2/KOH/\Delta$
  3. $H_2/Ni$
  4. $Zn(Hg)/conc.\,HCl$
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Correct answer: D. $Zn(Hg)/conc.\,HCl$

Acidic conditions ($Zn$ amalgam + conc. HCl). Reduces ketones/aldehydes all the way to methylene. Use Wolff–Kishner instead if the substrate is base-stable but acid-sensitive.

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**Wolff–Kishner reduction** uses which reagent to convert $>C=O$ to $>CH_2$?

  1. $NH_2NH_2$ then $KOH/\Delta$
  2. $O_3/Zn$
  3. $NaBH_4$
  4. $Zn(Hg)/HCl$
Show answer and solution

Correct answer: A. $NH_2NH_2$ then $KOH/\Delta$

$>C=O \xrightarrow{NH_2NH_2} >C=N-NH_2 \xrightarrow{KOH, \Delta} >CH_2 + N_2\uparrow$. Basic conditions — ideal when the substrate cannot tolerate the acidic Clemmensen conditions.

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