Question

Differentiate between primary, secondary and tertiary alcohols, showing their structure. In the presence of which enzyme does glucose convert to ethyl alcohol? (3+1)

Hint:

Classify by the number of carbons bonded to the C-OH carbon (one, two, three). The yeast enzyme that ferments glucose to ethanol is zymase.

Answer 1

Concept: Alcohols are classified by the number of carbon atoms directly attached to the carbon that carries the \(-OH\) group (the carbinol carbon).

Step 1 (Primary, 1° alcohol): The \(-OH\) bearing carbon is joined to only one other carbon atom. General form \(R-CH_2-OH\).
Example: Ethanol, \(CH_3-CH_2-OH\).

Step 2 (Secondary, 2° alcohol): The \(-OH\) bearing carbon is joined to two other carbon atoms. General form \(R_2CH-OH\).
Example: Propan-2-ol, \(CH_3-CH(OH)-CH_3\).

Step 3 (Tertiary, 3° alcohol): The \(-OH\) bearing carbon is joined to three other carbon atoms. General form \(R_3C-OH\).
Example: 2-methylpropan-2-ol, \((CH_3)_3C-OH\).

Step 4 (Enzyme): Glucose is converted to ethyl alcohol (ethanol) by the enzyme zymase:
\[C_6H_{12}O_6 \xrightarrow{\text{zymase}} 2\,C_2H_5OH + 2\,CO_2\]
\[\boxed{\text{Enzyme} = \text{zymase}}\]