Explore the alkoxy functional group. Learn what the alkoxy group is. Review its general formula and examples. Explore the alkyl group list to name the alkoxy group.
Updated: 01/31/2022
Alkoxy Group Overview and Examples
Alkoxy Group
An alkoxy group is a functional group whose primary constituents are oxygen, carbons, and hydrogens. A functional group is a chemical substituent that is attached to the main organic chain. It is a characteristic substituent that is made of different molecules attached to the organic carbon backbone. It carries the chemical properties of the organic molecule, which is why organic compounds are classified according to their functional groups. The alkoxy group is composed of an oxygen atom attached to an organic carbon chain. The word alkoxy combines two different terms:
- The word alk- is derived from the word alkyl.
- The word -oxy is derived from oxygen.
The general formula for the alkoxy group is {eq}-OR {/eq}, where R is the alkyl group, which is a hydrocarbon chain that is solely made of carbon and hydrogen atoms. The oxygen atom forms a single covalent bond with the carbon in the alkyl group. The alkoxy functional group is alternatively known as the alkyloxy group.
Alkyl Group List
The alkyl group is one of the two main constituents of the alkoxy group. It is an organic carbon chain that is made of nothing but carbon and hydrogen atoms. The absence of atoms different from C and H is the reason the alkyl group is classified as a hydrocarbon substituent. The alkyl group list is documented in Table 1, which shows the names of the alkyl groups and their corresponding chemical formulas.
All Things Alkoxy: An Overview
What do methoxy, ethyoxy, and alkyloxy all have in common? Besides the tongue twisting nature of pronouncing each name, they are all examples of alkoxy groups. An alkoxy group is an organic functional group that contains an alkyl group attached to an oxygen atom.
I know you are probably thinking, what an overloaded definition! Well, an organic functional group is the portion of a chemical compound that is a recognizable (or classifiable) group. Shown below is a table of very common functional groups. Do you see the alkyl group? An alkyl group contains only carbon and hydrogen atoms.
 |
The molecular formula for an alkoxy group is R-O. 'R' represents the alkyl group that is attached to the oxygen atom. Going back to our definition, we can see that alkoxy is a type of functional group because we can identify the alkyl portion in its molecular formula.
Naming alkoxy groups is a very easy process. But to understand naming we need to revisit our friend, the alkyl group. When naming a compound that contains an alkyl group, you must first determine how many carbon atoms are present in a linear chain. This number corresponds to the prefix within the chemical name. A list of common prefixes is shown below. To complete the name, you add the suffix '-yl' to the prefix.
For example, if a compound has a linear chain of five carbon atoms, this corresponds to the prefix 'penta.' Adding the suffix '-yl,' this alkyl group would be named pentyl. We follow a similar process when naming alkoxy groups. The only exception is a change to the suffix ending, where you add '-oxy' to the prefix as opposed to '-yl.'
| Alkyl Group | Chemical Formula | No. of C atoms |
|---|---|---|
| Methyl | -CH3 | 1 |
| Ethyl | -CH2CH3 | 2 |
| Propyl | -(CH2)2CH3 | 3 |
| Butyl | -(CH2)3CH3 | 4 |
| Pentyl | -(CH2)4CH3 | 5 |
| Hexyl | -(CH2)5CH3 | 6 |
| Heptyl | -(CH2)6CH3 | 7 |
| Octyl | -(CH2)7CH3 | 8 |
| Nonyl | -(CH2)8CH3 | 9 |
| Decyl | -(CH2)9CH3 | 10 |
Examples of Alkoxy Group Attached to Compounds
The alkoxy group {eq}-OR {/eq} is a functional group, which means it is not observed as an independent organic molecule, but a substituent that is attached an organic compound. Figure 1 and Figure 2 show examples of compounds that contain the alkoxy group.
 |
 |
The compound in the right side of Figure 1 is an ether. The oxygen atom separates the parent alkyl chain from the alkyl in the alkoxy group. The reason the smaller alkyl chain was selected to be a part of the alkoxy group is because the R in the alkoxy group must always be smaller than the R in the parent chain. The number of carbons in the parent chain must always be larger than the number of carbons in a substituent.
The figures show that the alkoxy group can be attached to different compounds; it can be attached to an aromatic ring (Figure 1, left), an aliphatic chain (Figure 1, right), a cyclic compound (Figure 2, left), and even a compound with a different functional group (Figure 2, right).
Naming Alkoxy Group
The naming of alkoxy groups is done by simply counting the number of carbons in the alkyl chain, assigning the correct prefix, then adding the suffix -oxy. Table 2 shows the prefixes and the corresponding number of carbon atoms. If the alkyl part was composed of 7 carbon atoms, the prefix hept- is used. Combining the prefix hept- with the suffix -oxy gives "heptoxy." An alkoxy group made of 7 carbon atoms is called heptoxy. An alkoxy group that is made of 5 carbon atoms is called pentoxy.
To differentiate between the alkane parent chain and the alkyl in the alkoxy functional group:
- Count the number of carbon atoms in each alkyl group. The alkyl groups are segregated by an oxygen atom.
- The larger alkyl group is the parent chain. The smaller alkyl group is a part of the alkoxy {eq}-OR {/eq} group.
Figure 3 shows an example of an alkoxy group attached to a regular alkane chain. The parent chain is the alkyl group that is made of a larger number of carbons. The alkyl group is made of three carbons, while the alkane in the parent chain is made of four carbons. The alkoxy group in this molecule is propoxy {eq}CH_3CH_2CH_2O- {/eq} and not butoxy {eq}CH_3CH_2CH_2CH_2O- {/eq}.
 |
| Prefix | No. C Atoms | Alkoxy Group Name |
|---|---|---|
| Meth- | 1 | Methoxy |
| Eth- | 2 | Ethoxy |
| Prop- | 3 | Propoxy |
| But- | 4 | Butoxy |
| Pent- | 5 | Pentoxy |
| Hex- | 6 | Hexoxy |
| Hept- | 7 | Heptoxy |
| Oct- | 8 | Octoxy |
| Non- | 9 | Nonoxy |
| Dec- | 10 | Decoxy |
Reactions of Alkoxy Group Compounds
Compounds with an alkoxy group undergo various chemical reactions. The alkoxy group in these compounds participate in reactions where the following compounds are formed:
- Alcohols, which are organic molecules that contain at least one hydroxyl group {eq}-OH {/eq}.
- Ethers, which are organic molecules with the structural formula {eq}R-O-R {/eq}. Their functional group is the alkoxy group. The alkoxy group can be attached to an alkyl or an aryl group. An aryl group is a cyclic aromatic ring that is characterized by having conjugated double bonds. An example of such is the benzene ring.
- Alkoxide ions, which are organic carbon atoms bonding to a negatively charged oxygen atom.
The addition of a hydrogen atom to the oxygen in the alkoxy group results to the formation of alcohol, as depicted in Figure 4. Ethers are formed when an alkoxy group is combined with an alkyl group. The alkoxide ion is basically a negatively charged alkoxy group {eq}RO^- {/eq}. The oxygen atom is carrying the negative charge.
 |
Production of Alkoxy Group
The alkoxy group can be produced from alcohols by simply removing the hydrogen atom participating in the {eq}O-H {/eq} bond in the hydroxyl group, as depicted in Figure 5. The reaction shows how butanol is converted to butoxy. The hydrogen in the hydroxyl group is removed, this leads to the formation of the alkoxy counterpart of this alcohol, the conversion of butanol to butoxy.
 |
Lesson Summary
A functional group is a substituent molecule attached to an organic carbon backbone. Organic molecules inherit their chemical properties from their functional group. An alkoxy group is one of the many functional groups encountered in organic chemistry. An alkoxy group is a functional group that is made of an oxygen atom attached to an alkyl group, which is a group that is composed of hydrogen and carbon atoms only. The general formula for the alkoxy group is {eq}-OR {/eq}. The alkyl side chain R is always made of a smaller number of carbons than the parent chain. The nomenclature of alkoxy groups is simply combining the alkyl prefix with the suffix -oxy. For example, if the alkyl group was made of 5 carbon atoms, then the prefix pent- is used. An alkoxy group whose alkyl group is made of 5 atoms is called pentoxy. The alkoxy group participates in reactions where the following is formed:
- Alcohols, which are organic molecules whose functional group is the hydroxyl group {eq}-OH {/eq}.
- Ethers, which are organic molecules made when an alkoxy group binds to an alkyl or an aryl group. Ethers' general formula is {eq}R-O-R {/eq}.
- Alkoxide ions, which are negatively charged alkoxy groups. The oxygen in the alkoxy group carries the negative charge.
Alkoxy groups can be synthesized from alcohols, like heptanol, butanol, and so on. This is done when the hydrogen atom in the hydroxyl group {eq}-OH {/eq} is removed. This leads to the formation of an alkoxy group of the alcohol molecule. The alkoxy group would have the same number of carbons in its alkyl group as the alcohol because the alcohol simply lost the hydrogen in its {eq}-OH {/eq}. Heptanol would turn into heptoxy group and butanol would turn into butoxy group.
 |
Alkoxy Groups as the Reactant and Product
The alkoxy group is commonly formed as a fragment from chemical compounds. In particular, this fragment arises when a chemical compound undergoes a reaction resulting in the removal of its hydrogen atom. In order to form an alkoxy group, this hydrogen atom must be attached to an oxygen atom. The illustration shown below describes how an alkoxy group can be formed from alcohol.
 |
Just as an alkoxy group is formed (i.e. becoming a product), it is also used to create other compounds (i.e. acting as a reactant). There are three compounds in particular: alcohol, ether, and the alkoxide ion. In a reversal of the equation shown above, alkoxy groups can bind to a hydrogen atom and form alcohol compounds. Ether compounds are formed when an alkoxy group binds to another alkyl group. Lastly, an alkoxy group carrying a negative charge is known as an alkoxide ion. Whether the alkoxy group is the reactant or the product, if you know how to spot its molecular formula (R-O) identifying alkoxy is easy to do.
Spotting an Alkoxy Group: Examples
There are a wide variety of alkoxy groups. Remember our friends methoxy, ethyoxy, and alkyloxy? We can classify them as alkoxy groups. Let's look at a few chemical compounds using the examples shown below. As a tip, always look for the oxygen atom first within the structure. Think of the oxygen atom as your compass guiding you towards finding and determining the location of the alkoxy group.
Example #1: Methoxyethane
 |
Locating the oxygen atom, you will see that it is bonded to a Ch3 (methyl) and Ch2Ch3 (ethyl). However, the chemical name provides a hint about where the alkoxy group is located in the structure. The term, 'methoxy-' tells you that the alkoxy group corresponds to the oxygen atom bonded to the Ch3. Don't be afraid to use the chemical name as a reference when locating alkoxy groups, if possible.
Example #2: 3-isopropoxy-1-butanol
 |
The oxygen atom is located between two Ch groups. Be careful not to choose the oxygen atom bonded to the hydrogen atom since that is an alcohol. Using the chemical name, we can see the alkoxy group is, 'isopropoxy-.' This refers to an alkoxy group whose oxygen atom is attached to three carbon atoms only.
Example #3: Phenetole
 |
Were you able to spot the alkoxy group? This is a trick example because there is no true alkoxy group to identify, which you might have realized based on the chemical name. Recall that alkoxy groups can be used to create compounds. In this case, by locating the oxygen atom we see that an alkoxy group is present in the form of an ether. Remember that an ether is formed from an alkoxy group bonded to an alkyl group.
The takeaway from these examples is that you can find an alkoxy group by locating the oxygen atom and determining what it is bound to. Alkoxy groups only bind to one R group. If bound to an additional R group, a light bulb should go off telling you alkoxy was used to create a compound. Lastly, whenever possible, use the chemical name as a guide. Following these tips, the next time you encounter a chemical, identification of the alkoxy group (or its derivatives) will be a breeze.
Lesson Summary
Alkoxy is a functional group that has an oxygen atom bonded to an R group. This R group is referred to as an alkyl group. The molecular formula is R-O. Naming of alkoxy groups involves adding the suffix '-oxy' to a chemical name. Alkoxy groups can be formed as fragments from chemical compounds or used to create chemical compounds. Examples of chemicals containing alkoxy groups include methoxyethane and 3-isopropoxy-1-butanol.
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All Things Alkoxy: An Overview
What do methoxy, ethyoxy, and alkyloxy all have in common? Besides the tongue twisting nature of pronouncing each name, they are all examples of alkoxy groups. An alkoxy group is an organic functional group that contains an alkyl group attached to an oxygen atom.
I know you are probably thinking, what an overloaded definition! Well, an organic functional group is the portion of a chemical compound that is a recognizable (or classifiable) group. Shown below is a table of very common functional groups. Do you see the alkyl group? An alkyl group contains only carbon and hydrogen atoms.
|
The molecular formula for an alkoxy group is R-O. 'R' represents the alkyl group that is attached to the oxygen atom. Going back to our definition, we can see that alkoxy is a type of functional group because we can identify the alkyl portion in its molecular formula.
Naming alkoxy groups is a very easy process. But to understand naming we need to revisit our friend, the alkyl group. When naming a compound that contains an alkyl group, you must first determine how many carbon atoms are present in a linear chain. This number corresponds to the prefix within the chemical name. A list of common prefixes is shown below. To complete the name, you add the suffix '-yl' to the prefix.
For example, if a compound has a linear chain of five carbon atoms, this corresponds to the prefix 'penta.' Adding the suffix '-yl,' this alkyl group would be named pentyl. We follow a similar process when naming alkoxy groups. The only exception is a change to the suffix ending, where you add '-oxy' to the prefix as opposed to '-yl.'
|
Alkoxy Groups as the Reactant and Product
The alkoxy group is commonly formed as a fragment from chemical compounds. In particular, this fragment arises when a chemical compound undergoes a reaction resulting in the removal of its hydrogen atom. In order to form an alkoxy group, this hydrogen atom must be attached to an oxygen atom. The illustration shown below describes how an alkoxy group can be formed from alcohol.
|
Just as an alkoxy group is formed (i.e. becoming a product), it is also used to create other compounds (i.e. acting as a reactant). There are three compounds in particular: alcohol, ether, and the alkoxide ion. In a reversal of the equation shown above, alkoxy groups can bind to a hydrogen atom and form alcohol compounds. Ether compounds are formed when an alkoxy group binds to another alkyl group. Lastly, an alkoxy group carrying a negative charge is known as an alkoxide ion. Whether the alkoxy group is the reactant or the product, if you know how to spot its molecular formula (R-O) identifying alkoxy is easy to do.
Spotting an Alkoxy Group: Examples
There are a wide variety of alkoxy groups. Remember our friends methoxy, ethyoxy, and alkyloxy? We can classify them as alkoxy groups. Let's look at a few chemical compounds using the examples shown below. As a tip, always look for the oxygen atom first within the structure. Think of the oxygen atom as your compass guiding you towards finding and determining the location of the alkoxy group.
Example #1: Methoxyethane
|
Locating the oxygen atom, you will see that it is bonded to a Ch3 (methyl) and Ch2Ch3 (ethyl). However, the chemical name provides a hint about where the alkoxy group is located in the structure. The term, 'methoxy-' tells you that the alkoxy group corresponds to the oxygen atom bonded to the Ch3. Don't be afraid to use the chemical name as a reference when locating alkoxy groups, if possible.
Example #2: 3-isopropoxy-1-butanol
|
The oxygen atom is located between two Ch groups. Be careful not to choose the oxygen atom bonded to the hydrogen atom since that is an alcohol. Using the chemical name, we can see the alkoxy group is, 'isopropoxy-.' This refers to an alkoxy group whose oxygen atom is attached to three carbon atoms only.
Example #3: Phenetole
|
Were you able to spot the alkoxy group? This is a trick example because there is no true alkoxy group to identify, which you might have realized based on the chemical name. Recall that alkoxy groups can be used to create compounds. In this case, by locating the oxygen atom we see that an alkoxy group is present in the form of an ether. Remember that an ether is formed from an alkoxy group bonded to an alkyl group.
The takeaway from these examples is that you can find an alkoxy group by locating the oxygen atom and determining what it is bound to. Alkoxy groups only bind to one R group. If bound to an additional R group, a light bulb should go off telling you alkoxy was used to create a compound. Lastly, whenever possible, use the chemical name as a guide. Following these tips, the next time you encounter a chemical, identification of the alkoxy group (or its derivatives) will be a breeze.
Lesson Summary
Alkoxy is a functional group that has an oxygen atom bonded to an R group. This R group is referred to as an alkyl group. The molecular formula is R-O. Naming of alkoxy groups involves adding the suffix '-oxy' to a chemical name. Alkoxy groups can be formed as fragments from chemical compounds or used to create chemical compounds. Examples of chemicals containing alkoxy groups include methoxyethane and 3-isopropoxy-1-butanol.
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Frequently Asked Questions
What is the alkoxy functional group?
An alkoxy functional group is a substituent that is made of an oxygen atom that is bonded to an alkyl chain R. The general formula for an alkoxy group is -OR.
How do you name an alkoxy group?
The first step in naming an alkoxy group is recognizing the alkyl chain and assigning the correct prefix for the alkyl group. The alkyl prefix relates to the number of carbon atoms that make the alkyl chain. If there were were 5 carbons, then the prefix pent- is used. If there were 6 carbons, then the prefix hex- is used. After assigning the prefix, combine it with the suffix -oxy. Example: pentoxy, hexoxy.
Is ethoxy a functional group?
Ethoxy is an alkoxy functional group. The prefix eth- indicates that there are two carbon atoms in the alkyl part R in alkoxy. This means that the chemical formula for an ethoxy functional group is CH3CH2O-.
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BackAlkoxy Group Overview & Examples | What is an Alkoxy Group?
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