A typical respiratory reaction is the oxidation of glucose C 6 H 12 O 6 , a simple sugar. Inside the body, the reaction is controlled to harvest the energy released so that it can be utilized for the production of ATP. Some of the energy released is also used to generate heat for the organism, but not in the rapid form of a combustion reaction that produces fire. Note that in redox reactions involving hydrocarbons, that they hydrogens are usually removed with the electrons.
Thus, they can be used as an indicator for which molecules are being oxidized and which are being reduced.
For example, in the reaction above the glucose molecule C 6 H 12 O 6 is losing the hydrogens as it is converted to carbon dioxide. As the glucose losing the hydrogens, it is also losing electrons and thus, the glucose is the oxidized component.
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Similarly, the oxygen on the reactant side is being converted into the water on the product side where it is gaining the hydrogens, and also gaining electrons. Thus, in this reaction, the oxygen is being reduced to water. Note that reaction classifications can also overlap and fall into more than one category.
For example, the hydrogenation reaction presented above in the removal of carbon-carbon double bonds is also an example of a redox reaction. In that reaction, the hydrocarbons are gaining hydrogens and also electrons, as the double bonds are removed forming the saturated hydrocarbons. Thus, the TAGs are being reduced in this reaction.
Chemical bonds and reactions
In this case, the oxidized component H 2 is being entirely used up in this process. As seen above, organic molecules that contain a lot of carbon and hydrogen bonds have high energy potential and ability to be oxidized to CO 2 and water. In this section, we will cover the oxidation potential of organic molecules with oxygen-containing functional groups. Alcohol functional groups contain the greatest oxidative potential of all the oxygen containing functional groups. The reactivity of alcohols depend on the number of carbon atoms attached to the specific carbon atom that is attached to the -OH group.
Alcohols can be grouped into three classes on this basis. Some alcohols can undergo oxidation reactions. Remember in redox reactions, the component of the reaction that is being oxidized is losing electrons LEO while the molecule receiving the electrons is being reduced GER. In organic reactions, the flow of the electrons usually follows the flow of the hydrogen atoms.
Thus, the molecule losing hydrogens is typically also losing electrons and is the oxidized component. The molecule gaining electrons is being reduced. For alcohols, both primary and secondary alcohols can be oxidized.
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Tertiary alcohols, on the other hand, cannot be oxidized. In many oxidation reactions the oxidizing agent is shown above the reaction arrow as [O]. The oxidizing agent can be a metal or another organic molecule. In the reaction, the oxidizing agent is the molecule that is reduced or accepts the electrons. In alcohol oxidation reactions, the hydrogen from the alcohol and a hydrogen that is attached to the carbon that has the alcohol attached, along with their electrons, are removed from the molecule by the oxidizing agent. Removal of the hydrogens and their electrons results in the formation of a carbonyl functional group.
In the case of a primary alcohol, the result is the formation of an aldehyde. In the case of a secondary alcohol, the result is the formation of a ketone. Note that for a tertiary alcohol, that the carbon attached to the alcohol functional group does not have a hydrogen atom attached to it.
Thus, it cannot undergo oxidation. When a tertiary alcohol is exposed to an oxidizing agent, no reaction will occur. Notice that for the primary alcohol that undergoes oxidation, that it still retains a hydrogen atom that is attached to the carbonyl carbon in the newly formed aldehyde. This molecule can undergo a secondary oxidation reaction with an oxidizing agent and water, to add another oxygen atom and remove the carbonyl hydrogen atom.
This results in the formation of a carboxylic acid. Write an equation for the oxidation of each alcohol. Use [O] above the arrow to indicate an oxidizing agent. The first step is to recognize the class of each alcohol as primary, secondary, or tertiary. This alcohol has the OH group on a carbon atom that is attached to only one other carbon atom, so it is a primary alcohol. Oxidation forms first an aldehyde and further oxidation forms a carboxylic acid.
This alcohol has the OH group on a carbon atom that is attached to three other carbon atoms, so it is a tertiary alcohol. No reaction occurs. This alcohol has the OH group on a carbon atom that is attached to two other carbon atoms, so it is a secondary alcohol; oxidation gives a ketone. As shown above in the alcohol section, aldehydes can undergo oxidation to produce a coarboxylic acid. This is because the carbonyl carbon atom still retains a hydrogen atom that can be removed and replaced with an oxygen atom. Ketones on the other hand, do not contain a hydrogen atom bound to the carbonyl carbon atom.
Thus, they cannot undergo further oxidation. As noted above, ketones that are exposed to an oxidizing agent will have no reaction. Reduction reactions with aldehydes and ketones revert these compounds to primary alcohols in the case of aldehydes and secondary alcohols in the case of ketones. They are essentially the reverse reactions of the alcohol oxidation reactions. For example, with the aldehyde, ethanal you get primary alcohol, ethanol:.
In general terms, reduction of an aldehyde leads to a primary alcohol. Reduction of a ketone, such as propanone will give you a secondary alcohol, such as 2-propanol:. Reduction of a ketone leads to a secondary alcohol. Methanol is quite poisonous to humans. Ingestion of as little as 15 mL of methanol can cause blindness, and 30 mL 1 oz can cause death. However, the usual fatal dose is to mL. Formaldehyde reacts rapidly with the components of cells, coagulating proteins in much the same way that cooking coagulates an egg.
This property of formaldehyde accounts for much of the toxicity of methanol. Organic and biochemical equations are frequently written showing only the organic reactants and products. In this way, we focus attention on the organic starting material and product, rather than on balancing complicated equations. Ethanol is oxidized in the liver to acetaldehyde:. The acetaldehyde is in turn oxidized to acetic acid HC 2 H 3 O 2 , a normal constituent of cells, which is then oxidized to carbon dioxide and water.
However, it should be noted that acetaldehyde is toxic and can build up to dangerous levels with chronic, high use of alcohol. The liver is the major site for alcohol metabolism, thus, chronic drinking can lead to liver cirrhosis, a dangerous disease that converts normal liver tissue into scar tissue that can no longer function.
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Ethanol itself can also be toxic to humans. The rapid ingestion of 1 pt about mL of pure ethanol would kill most people, and acute ethanol poisoning kills several hundred people each year—often those engaged in some sort of drinking contest. Ethanol freely crosses into the brain, where it depresses the respiratory control center, resulting in failure of the respiratory muscles in the lungs and hence suffocation. Ethanol is believed to act on nerve cell membranes, causing a diminution in speech, thought, cognition, and judgment.
It has a high vapor pressure, and its rapid evaporation from the skin produces a cooling effect. It is toxic when ingested but, compared to methanol, is less readily absorbed through the skin and can thus be used topically for muscle soreness. Overall, the processes of oxidation and reduction are critical for life. This is because the oxidation of our food molecules provides enough energy for the cells in our body to recycle the major source of energy for cellular metabolism and other energetic reactions required for life, adenosine triphosphate ATP Figure 7.
This is also a major building block for RNA biosynthesis. When the phosphate bonds are hydrolyzed to produce ADP and water, there is a large release of energy.https://grupoavigase.com/includes/169/4776-hombre-32.php
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The ability of the ATP phosphoester bonds to undergo hydrolysis is the reason it is such a great energy source! The average human will typically use their body weight in ATP every day kg!! This means that each ATP molecule must be recycled between times each day! ATP is the main energy source within the body. Cleavage of the high energy phosphate bonds releases large amounts of energy that are used for neuron function, muscle contraction, and other metabolic processes in the body.
In fact, so much energy is needed to run the human body that each ATP molecule must be recycled an average of times per day.
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