Key Difference – Acyl vs Alkyl
Almost all organic molecules in nature have functional groups in their structure, which determines the chemical and physical properties of those molecules. The terms alkyl and acyl refer to moieties (a portion) of large molecules. Alkyl and acyl can act as the functional groups of the main molecule. Both these groups contain carbon and hydrogen atoms. The key difference between alkyl and acyl groups is that acyl group has an oxygen atom attached with a double bond to the carbon atom whereas alkyl group has no oxygen atom attached to its carbon atoms.
CONTENTS
1. Overview and Key Difference
2. What is Acyl
3. What is Alkyl
4. Side by Side Comparison – Acyl vs Alkyl in Tabular Form
5. Summary
What is Acyl Group?
Acyl group is a functional group present in some organic molecules. It is composed of a carbon atom attached to a double bonded oxygen atom and an alkyl group. The acyl group can be easily recognized due to the presence of C=O double bond. There is a vacant space for another atom or a group to get attached to it. Acyl group is formed by the removal of a hydroxyl group of an oxoacid such as carboxylic acid. Normally, acyl groups are found in esters, aldehydes, ketones, acid chlorides, etc.
The general symbol for acyl group is given as RCO-. The carbocation made from an acyl group is RCO+. Here, the R group is attached to the carbon atom with a single bond whereas the oxygen atom is attached to the carbon atom with a double bond. A common example for a molecule containing an acyl group is acyl chlorides where acyl group is attached to a chloride atom. The R group can be an alkyl group or an aromatic ring.
Figure 01: Acyl Group
What is Alkyl Group?
Alkyl can be defined as a hydrocarbon radical. Alkyl group is also a functional group. It is composed only of carbon and hydrogen atoms. Unlike in acyl group, there are no oxygen atoms in alkyl group. Alkyl group is derived from an alkane. One hydrogen atom is removed from the alkane, so there is a vacant space for it to get attached to another atom or molecule. The general formula can be given as CnH2n+1.
Alkyl groups can also be substituted to aromatic rings. Alkyl groups can be grouped into few types according to the carbon that has the vacant space such as primary, secondary and tertiary. The name of the alkyl group is derived from the name of the corresponding alkane. Some of the common alkyl groups include methyl, ethyl, propyl, etc.
Figure 02: Alkyl Group
What is the difference between Acyl and Alkyl?
Acyl vs Alkyl |
|
| Acyl group is composed of an oxygen atom. | Alkyl group has no oxygen atom. |
| Origin | |
| Acyl group is derived from oxoacids. | Alkyl group is derived from alkanes. |
| Bonds | |
| Acyl group has a double bond essentially in between carbon atom and oxygen atom. | Alkyl group has no such double bond. |
| Hybridization | |
| Carbon atom in acyl group is sp2 hybridized | Carbon atom in alkyl group is sp3 hybridized. |
| Identification | |
| Compounds containing Acyl groups cause acidity in water when testing the pH solutions. | Compounds containing Alkyl groups does not cause acidity when pH solutions are tested. |
Summary – Acyl vs Alkyl Group
Acyl and alkyl groups act as functional groups when attached to a carbon chain. The main difference between acyl and alkyl group is that the acyl group has an oxygen atom attached to the carbon atom with a double bond whereas alkyl group has no oxygen atoms.
References:
1.Kennepohli, D., 2016. Libretexts. [Online] Available here [Accessed 30 05 2017].
2. Marie, A., n.d. ThoughtCo.. [Online] Available here [Accessed 30 05 2017].
Image Courtesy:
1. “Acyl group” (Public Domain) via Commons Wikimedia
2. “Isopropyl group” By Su-no-G – Own work. Made with CorelDRAW, not with ChemDraw. (Public Domain) via Commons Wikimedia
