Alcohols
Hiya!
Today I've got a very interesting topic on Alcohols! Maintain your (alcoholic) concentration and happy reading!
Alcohols are part of their very own homologous series and each have similar and yet different properties. As in any homologous series, alcohols have a functional group. The functional group of alcohols is the OH group. This functional group attaches to monomers called alkenes because they have a double carbon bond which means they are able to break this and create a new molecule. All alcohols end with the suffix 'ol' with the start of the word reflecting the number of carbons and hydrogens that make the other part of the alkene. (I explain alkenes and hydrocarbons in another blog so you should definitely check that out if you haven't). To formulate the alcohol, a hydrogen must be lost from the alkene and replaced with the functional group- in this case our OH molecule.
In every alcohol molecule;
Today I've got a very interesting topic on Alcohols! Maintain your (alcoholic) concentration and happy reading!
Alcohols are part of their very own homologous series and each have similar and yet different properties. As in any homologous series, alcohols have a functional group. The functional group of alcohols is the OH group. This functional group attaches to monomers called alkenes because they have a double carbon bond which means they are able to break this and create a new molecule. All alcohols end with the suffix 'ol' with the start of the word reflecting the number of carbons and hydrogens that make the other part of the alkene. (I explain alkenes and hydrocarbons in another blog so you should definitely check that out if you haven't). To formulate the alcohol, a hydrogen must be lost from the alkene and replaced with the functional group- in this case our OH molecule.
 |
| Some pretty funky looking drinks (Randy Fath) |
In every alcohol molecule;
- each carbon atom must form 4 bonds
- each hydrogen atom must form 1 bond
- each oxygen atom must from 2 bond
It's important to know the first few alcohols and their formations (just like learning the first few alkenes/alkanes) ;
-ethanol
-propanol
-butanol
-pentanol
-hexanol
But why do we have these alcohols and how are they produced? There are two main methods of alcohol production; fermentation and the hydration of alkenes. So what is involved with the fermentation? Fermentation is the anaerobic respiration of yeast.. Enzymes in the yeast break down the glucose molecules to form the carbon dioxide and ethanol molecules and energy is also released. Fermentation has to occur in controlled temperatures and anaerobic conditions in order for the process to occur correctly- if the temperatures are too high then the enzymes will denature and if the temperature is too low the enzymes will not function properly (but that's alcohol for you!). This process is often used in the production of beers, but ethanol can be used as a fuel and in solvents. Here is a list of pros and cons:
Alternatively, we can produce alcohols using the hydration of alkenes (hydrocarbons with double carbon bonds). Alkenes are reacted with water vapour and a catalyst (often phosphoric acid) to form any required alcohol (within boundaries). This process requires high energies and temperatures of up too 300 degrees Celsius. Using this method is very fast and can allow large yields of alcohols to be obtained quickly. However we must still assess the pros an cons:
-propanol
-butanol
-pentanol
-hexanol
But why do we have these alcohols and how are they produced? There are two main methods of alcohol production; fermentation and the hydration of alkenes. So what is involved with the fermentation? Fermentation is the anaerobic respiration of yeast.. Enzymes in the yeast break down the glucose molecules to form the carbon dioxide and ethanol molecules and energy is also released. Fermentation has to occur in controlled temperatures and anaerobic conditions in order for the process to occur correctly- if the temperatures are too high then the enzymes will denature and if the temperature is too low the enzymes will not function properly (but that's alcohol for you!). This process is often used in the production of beers, but ethanol can be used as a fuel and in solvents. Here is a list of pros and cons:
- Relatively low energy process (PRO)
- Cheap production of ethanol (PRO)
- Only produces small amount of ethanol (CON)
- Takes a long time to produce (CON)
- Only produces one type of alcohol (CON)
- relatively low yields (CON)
 |
| (Aaron Barnarby) |
Alternatively, we can produce alcohols using the hydration of alkenes (hydrocarbons with double carbon bonds). Alkenes are reacted with water vapour and a catalyst (often phosphoric acid) to form any required alcohol (within boundaries). This process requires high energies and temperatures of up too 300 degrees Celsius. Using this method is very fast and can allow large yields of alcohols to be obtained quickly. However we must still assess the pros an cons:
- Can produce yields quickly (PRO)
- Produces high yields of alcohol (PRO)
- Can produce any desired alcohol (PRO)
- Requires catalyst (CON)
- Requires high energy and temperatures maintained (CON)
- Made from crude oil and alkane cracking ~ non-renewable resource ~ (CON)
 |
| I'm a little too tired for a caption (Crystal Kwok) |
Reactions with alcohols. As we learn about the production of alcohols, it's also important we learn about where they fit in organic chemistry and their reactions with other chemicals/substances. There are four main reactions we study with alcohols.
- Combustion. The alcohols undergo complete combustion to from carbon dioxide gas and water. If the alcohols undergo incomplete combustion then carbon monoxide (a toxic gas) or carbon particulates are formed instead due to a lack of oxygen.
- Sodium reaction. As sodium is added into a solution of ethanol, the solutions bubbles due to the presence of hydrogen gas. The reaction of lithium and ethanol produces lithium ethoxide and hydrogen.
- Oxidation reaction. The alcohols can be oxidised instead of combusted to produce carboxylic acids (with the functional group COOH- don't worry I'll explain this in a different post). The ethanol reacts with the oxidising agent to produce ethanoic acid and water.
- Water solubility. We can mix different alcohols with water to test their solubility (ability to mix in completely). As the hydrocarbon alcohol chains increase in length it's notable that the solubility decreases.
Comments
Post a Comment