Ch. 2 - Molecular RepresentationsWorksheetSee all chapters
All Chapters
Ch. 1 - A Review of General Chemistry
Ch. 2 - Molecular Representations
Ch. 3 - Acids and Bases
Ch. 4 - Alkanes and Cycloalkanes
Ch. 5 - Chirality
Ch. 6 - Thermodynamics and Kinetics
Ch. 7 - Substitution Reactions
Ch. 8 - Elimination Reactions
Ch. 9 - Alkenes and Alkynes
Ch. 10 - Addition Reactions
Ch. 11 - Radical Reactions
Ch. 12 - Alcohols, Ethers, Epoxides and Thiols
Ch. 13 - Alcohols and Carbonyl Compounds
Ch. 14 - Synthetic Techniques
Ch. 15 - Analytical Techniques: IR, NMR, Mass Spect
Ch. 16 - Conjugated Systems
Ch. 17 - Aromaticity
Ch. 18 - Reactions of Aromatics: EAS and Beyond
Ch. 19 - Aldehydes and Ketones: Nucleophilic Addition
Ch. 20 - Carboxylic Acid Derivatives: NAS
Ch. 21 - Enolate Chemistry: Reactions at the Alpha-Carbon
Ch. 22 - Condensation Chemistry
Ch. 23 - Amines
Ch. 24 - Carbohydrates
Ch. 25 - Phenols
Ch. 26 - Amino Acids, Peptides, and Proteins
Johnny Betancourt

By definition, functional groups are specific groups of atoms commonly found across molecules all over the universe, that look and behave similarly when exposed to like conditions.

 P.S. Here’s my 5-minute video on memorizing the 17 most important functional groups.

P.S.S Here is the 49-minute super-comprehensive version if you are not in a time crunch.

INTRO: WHY DO WE NEED FUNCTIONAL GROUPS?

Functional groups are some of the first terms you learn to recognize in undergraduate organic chemistry- and they happen to be some of the most important. You’ll need many of these later, for example when you study carbohydrates and protein functional groups in biology.

In this post I’m going to teach you how to memorize them based on this chart:

The 17 most important functional groups chartThe 17 most Important Functional Groups Chart

 Why do we even need functional groups? There are quite literally infinite combinations of molecules found in the universe. We could spend the next 100 years learning the name and reactivity of each molecule separately OR we could try to find some patterns in the chaos. 

Functional groups are those patterns.

Specifically, when compared against each other, they share similarities in polarity, acidity, chemical reactivity, etc.

Thankfully, in undergraduate organic chemistry 1 you’re only going to be responsible to know ~17 of these specific groups. I’m about to give you the functional group run-down of your life, with examples and charts of how to memorize these.

(In Orgo 2 the list gets longer, and I’ll have a separate post for those.) 

HEADS UP: For this topic, I’m going to assume you already know how to represent molecules in skeletal (bond line/line angle) form. Meaning I’ll be dropping all hydrogens and lone pairs. If you still need help with understanding these, feel free to watch my videos on skeletal structure.

PART 1: MEMORIZING THE 17 MOST IMPORTANT FUNCTIONAL GROUPS

     1.     Hydrocarbons: Starting with the Backbone

Alkanes (C-C single covalent bonds) are the skeleton of organic chemistry. For that reason, alkanes are not actually considered functional groups, since they provide the backbone for everything else.

However, by mixing carbons and hydrogens together, you can get a few other combinations of carbon and hydrogen that are uniquely reactive. This is how we get alkenes (C=C double bonds) and alkynes (C≡C triple bonds).  

hydrocarbon-functional-groupsHydrocarbon Functional Groups

Benzene is the name of a 6-membered ring with alternating single and double bonds (like the Clutch Prep Logo), however “benzene” is not really a functional group since it is the name of a single molecule. The group is actually called aromatics or arenes. Thus, benzene is part of an aromatic functional group. We will learn more about the names of benzene derivatives later in the year . 

Remember: The “-R” symbol is used to represent extra hydrocarbon side chains on the molecule that we don’t particularly care about at that moment. 

When you extend benzene off of a carbon chain (-R), you get the side chain functional groups phenyl (directly attached to the main chain) and benzyl (extra –CH2 between the benzene and the main chain). These names are counterintuitive, since it makes logical sense that benzene connected to a main chain is called “benzyl”, but chemists aren’t always logical and that’s just plain wrong. 

I’m just the messenger! Take note. 

Now that we are done with hydrocarbons, let’s talk about carbonyls. 

Intermission: What is a carbonyl and why does it matter?  

Carbonyls are just C=O bonds on your molecule. They are NOT true functional groups since they are an essential component of many different functional groups. Some textbooks call them types of “moieties” (a bonding pattern) but I’m just going to call them carbonyls and expect you to remember that they are not functional groups. 


Carbonyl is not Technically a Functional GroupCarbonyl is not Technically a Functional Group


2. Functional Groups WITHOUT Carbonyls 

When you add single bonded heteroatoms (non-carbon atoms) to alkane chains, you end up getting a bunch of the most essential functional groups for organic chemistry. 

You’ll see soon why the “no carbonyls” part is important in a sec. Here’s the list:

 List of functional groups without carbonylsList of Functional Groups Without Carbonyls

  • When you add any halogen “-X” (Group 7a: -F, -Cl, -Br, -I) you get an alkyl halide (RX)
    • Also known as a haloalkane
    • Specifically called alkyl fluoride, alkyl chloride, alkyl bromide, alkyl iodide
  • When you add any –N (with hydrogens OR carbons attached) you get an amine 
  • When you add an –OH you get an alcohol (ROH)
  • When you add an –OR you get an ether (ROR)
    • Memory Trick: “I’m an ether, ROR! (like you are a scary dinosaur)” 
  • When you add an –SH you get a thiol (RSH)
  •  When you add a -C≡N you get a nitrile (RCN)

CATCH: There are actually several types or “degrees” of these functional groups, but we’ll have to save that for PART 2 (see below). For now, its enough that you just know these groups.


3. Functional Groups WITH Carbonyls

If you take the same functional groups we just memorized and place a carbonyl next to them, you get entirely new compounds.  

List of Carbonyl Functional GroupsList of Carbonyl Functional Groups

When you add a carbonyl to an alkane you actually get two functional groups:

  • When the carbonyl is on the end of carbon chain “terminal” it's called an aldehyde
  • When the carbonyl is in the middle of the carbon chain “internal” it's called a ketone

Now this is where things get interesting!

When you place carbonyls next to the heteroatom-containing functional groups we learned in point 2, many of the new functional groups are given similar names, so its easy to remember which functional groups pair up with which. 

  • Alkyl Halide + Carbonyl = Acid Halide aka Acyl Halide (COX)
    • Acyl chloride, acyl bromide, acyl iodide (acyl fluoride is rarely observed) 
  • Amine + Carbonyl = Amide (CONH3, CONRH2, CONR2H, CONR3
  • Alcohol + Carbonyl = Carboxylic Acid (COOH or CO2H)
  • Ether + Carbonyl = Ester (COOR or CO2R)

The odd man out is carboxylic acid, but as you can see, the names of the other three pairs are almost identical. As long as you remember the first functional group of each pair, you should be able to figure out the other one. 


4. Putting It All Together

The way I’ve organized this chart, similar groups are aligned horizontally and similar pairs are lined up vertically. Now its time for you to put this into practice. 

Can you name the 17 functional groups and fill in the blank spaces in the functional group table without looking above? 

Blank list of functional groupsBlank list of functional groups

Great job (I’m assuming you tried). Now, what’s the difference between a primary alcohol and a tertiary alcohol? We’re going to talk about how to name the degrees of each functional group.


PART 2: DETERMINING FUNCTIONAL GROUP DEGREE

The best way to introduce the concept of degrees is actually to go back to the example of hydrocarbons. 

Example of Hydrocarbon Degrees


Both carbons and hydrogens can be named as methyl (0°), primary (1°), secondary (2°), tertiary (3°), etc. 

The highlighted carbon and hydrogen in this example are both secondary (2), but for very different reasons. 

  • The carbon is secondary because it is directly attached to two other carbons 
  • The hydrogen is also secondary because it is connected to a carbon that is connected (indirectly attached) to two other carbons

See the difference? Hydrogens get their degree from the carbon they are attached to. 



 This rule can be generalized to other atoms and functional groups as well. 

  • Atoms that can form multiple bonds (i.e. C, N) derive degree from direct attachment
  • Atoms/groups that can only form one bond (i.e. –H, –X, –OH) derive degree from indirect attachment

Not all functional groups get degrees by the way. In my functional groups video module, I call the functional groups that get degrees the “A Team”, because they all start with the letter A.

  • Alcohol (R-OH)
  • Alkyl Halide (R-X)
  • Amine (NH3, NRH2, NR2H, NR3)
  • Amide (CONH3, CONRH2, CONR2H, CONR3)

Just by observing these condensed formulas, can you predict which of these groups will derive degree from direct attachment (like carbon) because they can form multiple combinations of bonds? 

If you said the nitrogen-containing functional groups, amine and amide, you are correct! Remember, I said that nitrogen-containing functional groups behave like carbon with respect to degree. 

Pop quiz, can you name the following examples of functional groups along with their degree? I’ve solved the first one for you (answers/explanations at bottom of the page):

 functional-groups-examplesFunctional Groups Examples

Here’s a video of Jonathan identifying functional groups in the gigantic anti-rejection molecule called everolimus (zortress). Can you find them all (including degrees)?

Functional Group Answers: 

2. Aldehyde. It is a carbonyl at the end of a chain with no heteroatoms next to it.

- Even though it starts with “A” sadly aldehyde is not on the A team!

3. Secondary (2°) amine because the nitrogen is directly attached to two carbons 

4. Ester. Looks more confusing in condensed formula, but you need to be able to recognize this. 

5. Primary (1°) alkyl halide (chloride) because the chlorine is indirectly attached to 1 carbon. 

- (Aka the carbon that the chlorine is attached to is only attached to 1 carbon) 

6. Tertiary (3°) amide because the nitrogen is directly attached to 3 carbons 

7. Methyl (0°) alcohol because the oxygen is indirectly attached to zero carbons

- (Aka the carbon that the oxygen is attached is not connected to any other carbons) 

8. Ether. I’m an ether, R-O-R!

9. Ketone. This is a carbonyl in the middle of a chain with no other heteroatoms next to it. Easy to recognize that this is a ketone.


Johnny Betancourt

Johnny got his start tutoring Organic in 2006 when he was a Teaching Assistant. He graduated in Chemistry from FIU and finished up his UF Doctor of Pharmacy last year. He now enjoys helping thousands of students crush mechanisms, while moonlighting as a clinical pharmacist on weekends.


Additional Problems
Identify all of the functional groups in Crixivan, an important drug in the treatment of AIDS.
For each of the molecules below write the name of the major functional group present on the line below each structure.
Identify ALL of the functional groups in the following molecule. Assign degree of functional group when appropriate.
Cyclic compounds of the general type shown here are called lactones. What functional group does a lactone contain?
Identify ALL of the functional groups in the following molecule. Assign degree of functional group when appropriate.
Circle the only alkene:
Which structure(s) contain(s) a tertiary amine?
Which structure contain(s) a tertiary alcohol?
Provide a LINE DRAWING that exemplifies each of the following functional groups below. Draw a real molecule, not just the generic formula using the letter “R”, and your molecule must contain exactly 5 carbons.  
Provide a LINE DRAWING that exemplifies each of the following functional groups below. Draw a real molecule, not just the generic formula using the letter “R”, and your molecule must contain exactly 5 carbons.
Draw a specific example of the Functional Group for each of the names listed below. You can use a methyl group in place of R for your example.
In the structure shown below, the functional groups in the triangle, rectangle, pentagon and circle (in this same order) are a) amine, ketone-ether, ether, amide b) amide, ester, ether, ketone-amine c) amine, ester, ether, amide d) amine, ester, ether, ketone-amine
Which of these molecules contains  amide, ketone, ether, and ester functional groups?
For each of the molecules below write the name of the major functional group present on the line below each structure. (SPELLING COUNTS)
Identify the functional groups in the following molecule: a. ketone, aromatic, 1° alcohol, ester b. aldehyde, 3° alcohol, aromatic, ketone c. ester, aromatic, 1° alcohol, 1° alcohol d. ketone, 1° alcohol, ether, aromatic e. aldehyde, ester, aromatic, 1° alcohol
Circle and label FOUR (4) different functional groups in the following molecule.
“Amoxicillin is an antibiotic useful for the treatment of a number of bacterial infections. It is the first line of treatment for middle ear infections.” (Wikipedia, 9/4/2015). CIRCLE and LABEL FOUR (4) different functional groups in the molecule.
Look at the entire structure of Nasonex. How many methyl groups are present in Nasonex? A. 0 B. 6 C. 2 D. 3 E. 4 F. 5 G. 6 H. 7 I. 8 J. None of these
Look at the entire structure of Lamisil. How many methylene groups are present in the structure of this molecule?   A. 0      E. 4      I. 8 B. 1      F. 5      J. None of these C. 2      G. 6 D. 3      H. 7
For the structure given below circle all tertiary carbons and star all primary carbons.
What functional group(s) are in the molecule below? a) Amide b) Ether c) Ketone d) Aldehyde e) Ester
Label the circled groups with the numbers that correspond to the following:  1 = Strained 7 membered ring system. 2 = Amide 3 = Ether 4 = sp2 hybridized carbon 5 = Carboxylic acid
Categorize the following functional groups (use primary, secondary, tertiary descriptions when appropriate).   
Capsaicin, found in peppers, has the following structure. What is the molecular formula for capsaicin? Identify the functional groups.
The structure of L-DOPA, the precursor to the neurotransmitters dopamine, norepinephrine, and adrenaline, is below. MARK all the FAMILIES to which this molecule belongs because of its functional groups. A. Alkane B. Alkene C. Arene D. Alcohol  E. Ether F. Amine  G. Ketone H. Carboxylic acid  I. Ester  J. Amide
For the following functional groups either (a) provide the name with correct spelling or (b) draw a molecule in skeletal form containing that functional group in the space provided.
Everolimus (Zortress) is a derivative of sirolimus and works similarly to sirolimus as an inhibitor of mammalian target of rapamycin (mTOR). It is currently used as an immunosuppressant to prevent rejection of organ transplants (kidney and liver) and treatment of renal cell cancer and other tumours. Identify ALL of the functional groups present in everolimus, indicating  degree of the functional group when appropriate. 
Consider the structure below and answer the following questions. 
Categorize the following functional groups (use primary, secondary, tertiary descriptors when appropriate). 
The alkane below has how many 1o, 2o, 3o, 4o degree carbons:
Classify each of the following compounds as an alkane, alkene, alkyne, alcohol, aldehyde, amine, and so forth.  
Classify each of the following compounds as an alkane, alkene, alkyne, alcohol, aldehyde, amine, and so forth.
Which structure contains a 3° alkyl halide?  
Classify each of the following compounds as an alkane, alkene, alkyne, alcohol, aldehyde, amine, and so forth.
Classify each of the following compounds as an alkane, alkene, alkyne, alcohol, aldehyde, amine, and so forth.  
Classify each of the following compounds as an alkane, alkene, alkyne, alcohol, aldehyde, amine, and so forth.
Classify each of the following compounds as an alkane, alkene, alkyne, alcohol, aldehyde, amine, and so forth.  
Identify all of the functional groups in each of the following compounds:
Identify all of the functional groups in each of the following compounds:  
Identify all of the functional groups in each of the following compounds:
Identify all of the functional groups in each of the following compounds:  
The following compound is an intermediate in the synthesis of a gelator, which is a compound capable of self-assembling to form a gel in an organic liquid (Soft Matter 2012, 8, 5486–5492).  (a) Identify each functional group in the molecule. 
Identify all of the functional groups in each of the following compounds:
Many compounds with desirable medicinal properties are isolated from natural sources and are thus referred to as natural products. However, a compound’s medicinal properties are often known before the structure of the compound has been determined. Below are examples of compounds where the first proposed structure was incorrect (Angew. Chem. Int. Ed. 2005, 44, 1012–1044). In each case, the corresponding correct structure is also shown. Identify all functional groups in each pair of compounds and then compare the similarities and differences between their molecular structures. 
Identify all of the functional groups in each of the following compounds:
Many compounds with desirable medicinal properties are isolated from natural sources and are thus referred to as natural products. However, a compound’s medicinal properties are often known before the structure of the compound has been determined. Below are examples of compounds where the first proposed structure was incorrect (Angew. Chem. Int. Ed. 2005, 44, 1012–1044). In each case, the corresponding correct structure is also shown. Identify all functional groups in each pair of compounds and then compare the similarities and differences between their molecular structures. 
Identify all of the functional groups in each of the following compounds:
There are four alkyl bromides with the formula C 4H9Br. Write their structural formulas and classify each as to whether it is a primary, secondary, or tertiary alkyl bromide.
Classify the following alcohols as primary, secondary, or tertiary:  
Classify the following alcohols as primary, secondary, or tertiary:
Classify the following alcohols as primary, secondary, or tertiary:  
Classify the following alcohols as primary, secondary, or tertiary:
Classify the following alcohols as primary, secondary, or tertiary:  
Classify the following amines as primary, secondary, or tertiary:
Classify the following amines as primary, secondary, or tertiary:  
Classify the following amines as primary, secondary, or tertiary:
Classify the following amines as primary, secondary, or tertiary:  
Classify the following amines as primary, secondary, or tertiary:
Classify the following amines as primary, secondary, or tertiary:  
Write structural formulas for each of the following: (c) A secondary alcohol with the formula C3H6O.
Write structural formulas for each of the following: (d) A tertiary alcohol with the formula C4H8O.
How many tertiary hydrogens atoms are present in the molecule shown below?  a. six b. three c. one d. four
The compound  zoapatanol  was isolated from the leaves of a Mexican plant. Classify each oxygen in zoapatanol according to the functional group to which it belongs. If an oxygen is part of an alcohol, classify the alcohol as primary, secondary, or tertiary. 
In the molecule  shown below, how many primary alcohols are present? A) none B) 1 C) 2 D) 3 E) 4
In the molecule shown below, how many benzene rings are present? A) none B) 1 C) 2 D) 3 E) 4
Write structural formulas for each of the following: (g) Three secondary alkyl halides with the formula C5H11Br.
In the molecule shown below, how many secondary (2°) amines are present? A) none B) 1 C) 2 D) 3 E) 4
Consult Table 4.1 and classify each nitrogen-containing functional group in the anesthetic lidocaine according to whether it is an amide, or a primary, secondary, or tertiary amine. 
Write structural formulas for each of the following: (l) A secondary amine with the formula C3H9N.
Identify all of the functional groups in the following molecule.
Uscharidin is the common name of a poisonous natural product having the structure shown. Locate all of the following in uscharidin:   (a) Alcohol, aldehyde, ketone, and ester functional groups
The questions below refer to the structure of Zanamivir, which is shown below. This is a line-angle structure. Lone pairs are not shown explicitly, but every atom in this molecule has a formal charge of zero.  
Uscharidin is the common name of a poisonous natural product having the structure shown. Locate all of the following in uscharidin:  (b) Methylene groups 
Look at the  entire structure of Atenolol. How many  methylene groups are present in the structure of this molecule? A. 0 B. 1 C. 2 D. 3 E. 4 F. 5 G. 6 H. 7 I. 8 J. None of these
Uscharidin is the common name of a poisonous natural product having the structure shown. Locate all of the following in uscharidin:  (c) Primary carbons 
Identify ALL the functional groups in the following molecule, including their degree if applicable.
Identify ALL the functional groups in the following molecule, including their degree if applicable.
Identifying Functional Groups:
Identifying Functional Groups:
Identify the functional groups in the molecule of penicillin
Consider the compound below to answer the following questions. (a) How many methine hydrogens are there?   (b) How many primary Cs are there?   (c) Give the molecular formula of this compound.    (d) How many quaternary Cs are there?   (e) How many secondary alkyl groups exist as substituents?  
Identify the functional groups in the following molecule:
For the molecule pictured:i) Identify the circled functional groups;ii) How many lone pairs of electrons does this molecule have?iii) How many 1° hydrogens are present?iv) How many sp2 carbons are present?v) how many 3° carbons are present?vi) How many unit of unsaturation are present?
Identify the functional groups in the following molecule.
What is the name of the functional group attached at C5 for the molecule given below? (Hint: use the IUPAC name)A) chlorideB) methylC) ketoneD) isobutylE) benzyl
Identify the functional groups in the following molecule. 
For each of the molecules below write the name of the major functional group present on the line below each structure.
Identify all functional groups including degrees, if applicable, in this molecule. a) 2o Alcohol, 2o halide, Aldehyde, Ether, Alkyne and Alkene, 2o amine b) 2o amine, 2o alchohol, 1o halide, ketone, alkyne and alkene, ester c) Aldehyde, alkyne and alkene, 2o amine, ester, 1o alcohol, 1o halide d) 1o halide, alkyne and alkene, 2o alcohol, 1o amine, aldehyde, ester 
For the following structure
For the following structure:
Identify the functional group(s) in the following compound. 
Identify the functional group(s) in the following compound. 
Identify the functional group(s) that appear in betaxolol. This compound is in a class of drugs called beta-blockers, which are used to lower blood pressure, lower heart rate, reduce angina (chest pain), and reduce the risk of recurrent heart attacks. AlcoholEtherAreneCarboxylic AcidAldehydeEsterAmineAlkeneKetone 
Which functional group does not contain an oxygen atom? a. ketoneb. alcoholc. aldehyded. carboxylic acide. aminef. esterg. amideh. ether
Which is the correct structures for benzaldehyde 
What functional groups are present on this molecule? a. Carboxyl and aldehyde b. Hydroxyl and aldehyde c. Hydroxyl and ketone d. Hydroxyl and ester e. Carboxyl and ketone 
Select the compound below that contains a carboxylic acid functional group. a. CH3COOCH3b. CH3COOHc. CH3OCH3d. CH3COCH3 
Which of those compounds considered cyclic ether? 
Which of the following is a ketone?Select one:  
Which of the following compounds is a phenol?  
Which of the following is a tertiary amine? 
Which of the following in neither an aldehyde nor a ketone? Select one: 
The molecule below is largely responsible for the odor and flavor of pears. Which organic family is present ? 
Which compound is an ester? 
What common functional group in biomolecules is depicted in the figure below? (Where R represents any substituents.) a. Aldehyde b. Carbonylc. Ester d. Ketonee. Resehyde
Which of the following is a correct name for the following substance?Select one:a. benzeneb. benzaldehydec. phenold. benzaketonee. benzoic acid 
Identify all the functional groups found in vanillin?
Identify the following molecule as: A. an alcohol B. a phenol. C. an aromatic hydrocarbon. D. an acid.
What functional group is present in this compound? Select one:a. amineb. carboxylic acidc. alcohold. aldehydee. ketone 
Which of these compounds is a carboxylic acid? Select one:a. A, B and Cb. B onlyc. B and C onlyd. A and B onlye. A only 
Which of the following is tertiary amine?
Draw the structure(s) of all alkane(s) that have 6 carbons, 1 of which is tertiary.• You do not have to consider stereochemistry. • If more than one structure fits the description, draw them all. • Draw one structure per sketcher. Add additional sketchers using the drop-down menu in the bottom right corner. • Separate structures with + signs from the drop-down menu. 
Which of these molecules are alcohols? Check all that apply.