2.3 Functional Groups – Organic Chemistry I (2025)
Chapter 2: Fundamentals of Organic Structures
Functional groups are the most reactive parts in organic compounds and determine the major properties of compounds. A summary of common functional groups is included in Table 2.2. Knowing the functional groups well is one of the fundamental skills required for this course. This is required for students to quickly identify and name the functional groups included in molecules as well as to understand, interpret and draw the specific structure of each functional group clearly. The IUPAC naming of compounds containing several functional groups is required as well.
Alkene and alkynesare hydrocarbon functional groups; the π bond in multiple bonds accounts for the reactivity of alkenes and alkynes.
Benzene rings (C6H6) are a special type of hydrocarbon. Historically, because of the special aroma (sweet smell) that benzene and its derivatives release, they are called aromatic compounds. The structure of benzene can be represented as three C=C double bonds alternating with single bonds; however, the actual structure of benzene has nothing to do with alkenes. The structure of benzene, which is a big conjugation system, and the chemistry definitions of aromatic/aromaticity will be discussed in detail in Organic Chemistry II. Benzene rings can be shown with any of the following structure drawings.
When a halogen is connected with carbon, the group is called alkyl halide (orhaloalkane). The halide can be categorized as a primary (1°), secondary (2°) or tertiary (3°) halide, depending on what category the carbon connected with the halogen is in.
Alcohol is a functional group that you are probably familiar with. In organic chemistry, the term alcohol refers to a compound containing the OH (hydroxy) group. Depending on the position of the OH group, alcohols can also be categorized as primary (1°), secondary (2°) or tertiary (3°).
Another functional group that contains the oxygen atom in single bonds is ether. In ether, the O atom connects with two carbon-containing R groups through two C-O σ bonds. Compounds with ether as the only functional group are usually referred to with the common name “alkyl alkyl ether”. When the two alkyl groups are the same, they can be combined as “dialkyl”.
Ether can be in a cyclic structure as well. It may not be that intuitive to recognize the following structure as ether, and labelling the carbon atom will be helpful for identification.
Both nitrileand nitro groups contain nitrogen atoms, and they can be easily confused. Nitrile has a C≡N triple bond, and therefore can only be at the end of a structure, while nitro (NO2) can be in any position on the carbon chain or ring.
Amine is the organic derivative of ammonia, NH3. When the hydrogen atom(s) in NH3 is replaced with R groups, it produces amine. Amine can be primary (1°), secondary (2°) or tertiary (3°) depending on how many R groups are connected with nitrogen. Amines can also be referred to with common names.
For the functional groups in the 2nd part of Table 2.2, they all have a common structural unit of a carbonyl group C=O; the different structure of “W” in the general formula determines the nature of the functional group. It is usually more challenging to identify and draw these functional groups correctly because they are similar. More practice is needed.
Aldehydeand ketoneare similar in terms of their structures and properties. Aldehyde can be regarded as a special case of ketone since “H” can be regarded as an R with zero carbon. Because H has to be connected on one side of the C=O group in aldehyde, aldehyde can only be at the end of a structure. Ketone, on the other hand, must be in the middle position to ensure both sides of the C=O groups are connected with R groups. Ketone can also be in a cyclic structure.
The last four functional groups are related in terms of structures and chemical properties. When an OH group is connected with C=O, the whole COOH is called a carboxylic acid functional group. The other three: ester, anhydride and amide, are all derivatives of carboxylic acid, meaning they can be prepared with carboxylic acid as the starting material. For these three functional groups, it is important to remember that the “W” part has to be considered together with the C=O, since overall they define the functional group. For example, the COOR is ester; it can not be recognized as a “ketone” plus an “ether”.
The 7 major functional groups are: hydroxyl (such as alcohols, ROH), methyl (carbon-carbon bonds), carbonyl (carbon-oxygen double bonds), carboxyl (a combination of a carbonyl and hydroxyl group), amino (carbon-nitrogen bonds), phosphate (carbon, phosphate bonds), and sulfhydryl (carbon-sulfur bonds).
In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the rest of the molecule's composition.
If the compound includes more than one functional groups, the one with the highest priority is the “parent structure” and determines the “parent name”; the other groups will be regarded as “substituents”. “Suffix” is used to indicate the name of the parent structure, and “prefix” is for the substituent.
In organic chemistry, the most common functional groups are carbonyls (C=O. ), alcohols (-OH ), carboxylic acids (CO2H CO 2 H ), esters (CO2R CO 2 R ), and amines (NH2 ).
One of the easiest ways to learn functional groups is by making flash cards. Get a pack of index cards and write the name of the functional group on one side, and draw its chemical representation on the other. For now, a list of the most important ones you should know is provided here.
Functional groups will have different prefixes from their suffixes to distinguish them within the name. For example the amine functional group will use "-amine" as the suffix is it the highest priority group, but use the "amino-" prefix if it is the lower priority group as is a substituent. Hope that helps.
Common examples of functional groups are alcohols, alkenes, alkynes, amines, carboxylic acids, aldehydes, ketones, esters, and ethers, among others. In a typical sophomore organic chemistry course, there are about 15 key functional groups, with another group of 10 or so that make consistent appearances.
The structural features that make it possible to classify compounds into families are called functional groups. A functional group is a group of atoms within a molecule that has a characteristic chemical behavior. Chemically, a given functional group behaves in nearly the same way in every molecule it's a part of.
As a rule of thumb, the higher the oxidation state of the central carbon, the higher the priority of the functional group. Thus, carboxylic acids have higher priority than alcohols, and so on (See also table 21-1 in your textbook). 1. CARBOXYLIC ACIDS (highest priority among carbon-containing functional groups).
Functional groups have characteristic suffixes. Alcohols, for example, have 'ol' appended to the parent chain name, along with a number designating the location of the hydroxyl group. Ketones are designated by 'one'.
Organic molecules can be very large, often molecules contain more that one functional group. Consider the amino acid serine, shown in Figure 1.5. 1. Three functional groups are present in the molecule: an amine, an alcohol, and a carboxylic acid.
The functional theory of effective group decision making rests on the assumption that decision-making effectiveness is not affected by the production of certain communicative behaviors per se, but by the extent to which these fulfill the requirements for successful task completion.
Address: 5789 Michel Vista, West Domenic, OR 80464-9452
Phone: +97313824072371
Job: Education Orchestrator
Hobby: Lockpicking, Crocheting, Baton twirling, Video gaming, Jogging, Whittling, Model building
Introduction: My name is Rob Wisoky, I am a smiling, helpful, encouraging, zealous, energetic, faithful, fantastic person who loves writing and wants to share my knowledge and understanding with you.
We notice you're using an ad blocker
Without advertising income, we can't keep making this site awesome for you.
