How is ethyl alcohol prepared from starch? Give equation.

Understanding the initial phase in ethyl alcohol preparation starts with hydrolysis of starch. Starch, primarily found in plants like potatoes and corn, is a complex carbohydrate formed by the bonding of numerous glucose units. The hydrolysis process is akin to unlocking these units from their chain. Under the influence of water, acid, or enzymes like amylase, these bonds break effectively transforming starch into free-standing glucose molecules. This reaction can be expressed with the equation:
\[ (C_6H_{10}O_5)_n + nH_2O \rightarrow nC_6H_{12}O_6 \]
Through hydrolysis, we capitalize on the ample energy stored in starch for subsequent conversion into alcohol, highlighting the significance of this first step in the overall biochemical transformation.

Once we have glucose from the hydrolysis of starch, it undergoes glycolysis, a crucial energy-releasing pathway used by all forms of life. During glycolysis, glucose is methodically disassembled through a series of ten reactions. These reactions take place in the cytoplasm of cells and do not require oxygen, which qualifies glycolysis as an anaerobic process. The result of this series of chemical reactions is the formation of pyruvate.
The simplified equation representing glycolysis is: \[ C_6H_{12}O_6 \rightarrow 2C_3H_4O_3 + 2NADH + 2ATP \]
Energy is conserved in the form of NADH and ATP molecules, vital for the energy economy of the cell. By converting one molecule of glucose into two molecules of pyruvate, glycolysis sets the stage for the subsequent steps required to produce ethanol.

The journey from glucose to ethyl alcohol continues with the decarboxylation of pyruvate. This is where a carboxyl group, consisting of one carbon atom and two oxygen atoms, is elegantly removed from the molecule of pyruvate, releasing carbon dioxide in the process.
The relevant chemical equation is: \[ C_3H_4O_3 \rightarrow C_2H_4O + CO_2 \]
This step is significant in the transition from pyruvate to acetaldehyde, a simpler compound that is closer in structure to ethanol. Decarboxylation is primarily an anaerobic process which means it occurs in the absence of oxygen, typically in microbes during fermentation. It is an essential bridge between the sugar breakdown in glycolysis and the final reduction that will yield alcohol.

The final transformation in the synthesis of ethyl alcohol entails the reduction of acetaldehyde. In this stage, acetaldehyde acts as an acceptor of electrons and is reduced to ethanol, thanks to the presence of NADH, which functions as a reducing agent along with hydrogen ions.
The equation reflecting this process is: \[ C_2H_4O + NADH + H^+ \rightarrow C_2H_5OH + NAD^+ \]
This reduction reaction is the heart of the alcohol production phase, turning the somewhat reactive acetaldehyde into the more stable, energy-rich molecule of ethanol (ethyl alcohol). This entire process, from the initial hydrolysis of starch to the reduction of acetaldehyde, is fundamental in industries like brewing and biofuel production, showcasing the versatile application of biochemical pathways.