•

25 Dec 2025

•

4 pages

Understanding Carboxylic Acids - Chapter 26.3

sheila

@study_withsheila

Carboxylic acids are everywhere around you - from the vinegar... Show more

1 / 4

26.3- Carboxyuc Acids

Key Facts:
- functional group =
- COOH
R
C
O
H
- suffix =
-oic acid
- if there are 2
Carboxylic acid
groups =

Carboxylic Acids - Structure and Basics

The functional group that defines carboxylic acids is -COOH, which gives them their distinctive properties. When naming these compounds, you simply add the suffix -oic acid to the end (like ethanoic acid for vinegar).

If a molecule has two carboxylic acid groups, you use -dioic acid instead. Think of it as doubling up on the acidity! The general structure shows a carbon atom bonded to both a hydroxyl group $-OH$ and a carbonyl group $C=O$ .

The geometry around the carbon is particularly important - you'll find three regions of electron density creating bond angles of 120°, whilst the oxygen in the -OH group has two bonded pairs and two lone pairs, giving it a 104.5° angle.

Key Insight: The -COOH group combines two familiar functional groups (carbonyl and hydroxyl), which explains why carboxylic acids are so reactive and versatile.

Solubility and Physical Properties

Hydrogen bonding is the secret behind carboxylic acids' unique physical properties. The polar O-H bond allows these molecules to form strong hydrogen bonds with each other, creating dimers (pairs of molecules stuck together).

This hydrogen bonding also means carboxylic acids can bond effectively with water molecules. Carboxylic acids with up to 4 carbon atoms dissolve completely in water, but solubility drops dramatically as the carbon chain gets longer.

Here's the pattern you need to remember: longer carbon chains mean stronger London forces due to more electrons. This increases boiling points but decreases water solubility because the non-polar carbon chain dominates. However, if you've got more than one -COOH group, solubility increases again.

Exam Tip: Remember that melting and boiling points are unusually high for carboxylic acids due to that hydrogen bonding - this often comes up in exam questions!

Acid Behaviour and Reactions

Carboxylic acids are weak acids, which means they only partially dissociate in water. For example, methanoic acid (HCOOH) splits into H⁺ and HCOO⁻ ions, but not completely - that's why we use the equilibrium arrow.

Since they're acids, they undergo typical acid reactions. With metals, you get a salt plus hydrogen gas (a redox reaction). With bases, you get neutralisation reactions producing a salt plus water.

The naming pattern for the salts is straightforward - just change the '-oic acid' ending to '-oate'. So ethanoic acid becomes ethanoate, propanoic acid becomes propanoate, and so on.

Memory Aid: Think of carboxylic acids as "polite acids" - they donate protons, but not too aggressively, unlike strong acids like hydrochloric acid.

Specific Reactions You Need to Know

When carboxylic acids react with metals like magnesium, you get a classic redox reaction. For instance, propanoic acid + magnesium produces magnesium propanoate and hydrogen gas. The metal gets oxidised (loses electrons) whilst the hydrogen ions get reduced.

Neutralisation reactions follow predictable patterns. With metal oxides like calcium oxide, you get the metal carboxylate plus water. With hydroxides like sodium hydroxide, same result - salt plus water.

The test tube test for carboxylic acids uses sodium carbonate. If you add Na₂CO₃ to a carboxylic acid, you'll see fizzing as CO₂ gas is produced. This fizzing is your definitive test for the presence of a -COOH group.

Practical Note: That fizzing test with sodium carbonate is dead useful for identifying unknown compounds in your practicals - if it fizzes, you've likely got a carboxylic acid!

We thought you’d never ask...

What is the Knowunity AI companion?

Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.

Where can I download the Knowunity app?

You can download the app from Google Play Store and Apple App Store.

Is Knowunity really free of charge?

That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.

Most popular content in Chemistry

BTEC Applied Science Unit 1 Overview

Comprehensive resource for Year 12 students pursuing a Level 3 Diploma in Applied Science. This booklet covers essential topics including cell structure, chemical properties, and wave theory, providing clear explanations and key concepts to aid in your studies and exam preparation.

Chemistry

Paper 1 Flashcards for GCSE AQA Higher

Chemistry Paper 1 Flashcards for AQA Higher content

Chemistry

Chemistry paper 1 AQA

Condensed notes.

Chemistry

GCSE Chemistry Revision Notes

AQA GCSE Combined Chemistry * detailed summary

Chemistry

A-level OCR A Chemistry summary sheets

Everything from snaprevise for OCR chemistry a-level

Chemistry

Understanding Phase Transitions

Explore the key concepts of phase transitions in matter, including sublimation, melting, boiling, evaporation, and condensation. This summary covers the characteristics of solids, liquids, and gases, their unique properties, and the specific temperatures at which phase changes occur. Ideal for GCSE Chemistry students seeking to grasp the fundamentals of states of matter.

Chemistry

N5 Chemistry: Bonding & Reactions

Explore essential concepts in National 5 Chemistry, including atomic structure, types of bonding (ionic and covalent), reaction rates, and acid-base chemistry. This comprehensive guide covers key topics such as chemical equations, molarity, and neutralization reactions, providing a solid foundation for your studies.

Chemistry

GCSE Chemistry Overview

Explore key concepts in GCSE Chemistry, including atomic structure, chemical bonding, organic chemistry, and reaction rates. This comprehensive mindmap covers essential topics such as the Haber process, electrolysis, and energy changes, providing a clear understanding of the subject. Ideal for AQA Chemistry students preparing for exams.

Chemistry

Redox Reactions Overview

Explore the fundamentals of redox reactions, including oxidation states, definitions of oxidation and reduction, and the roles of oxidizing and reducing agents. This summary covers key rules for determining oxidation states, the concept of disproportionation, and practical applications in chemical equations. Ideal for A-Level Chemistry students preparing for exams.

Chemistry

Most popular content

An Inspector Calls: Character Insights

Explore in-depth analysis and key quotes for characters in J.B. Priestley's 'An Inspector Calls'. This resource covers Gerald Croft, Inspector Goole, Sheila Birling, Mrs. Birling, Eric Birling, and Eva Smith, focusing on themes of class, gender roles, and social responsibility. Ideal for students aiming for Grade 8 and above.

English Literature

aqa higher tier combined science - biology b1 : cell biology, paper 1

b1: cell biology - paper 1

Biology

Sociology of Families: Comprehensive Revision

Dive into an extensive overview of family dynamics, perspectives, and patterns in sociology. This resource covers key concepts such as family diversity, gender roles, marriage, and the impact of social policies on family structures. Perfect for A-Level Sociology students preparing for Paper 2.

Sociology

Comprehensive Crime & Deviance Overview

Explore an extensive revision of crime and deviance topics, including theories, types of crime, and the impact of media. This resource covers key concepts such as Marxism, functionalism, gender and crime, and the influence of globalization on criminal behavior. Ideal for students seeking a thorough understanding of criminology and its various theories. Type: Full Topic Revision.

Sociology

Sociology of Education Overview

Explore comprehensive A-Level Sociology notes on the education system, covering key theories, policies, and sociological perspectives. This resource includes insights on marketisation, gender roles, cultural deprivation, and educational inequalities, providing a thorough understanding of how education shapes social stratification and individual achievement. Ideal for exam preparation and in-depth study.

Sociology

Criminal Justice Evidence Rules

Explore the essential rules governing the use of evidence in criminal cases, including reliability, admissibility, and relevance. This summary covers key concepts such as the roles of personnel in investigations, the impact of witness testimonies, and the implications of plea bargaining. Ideal for Year 13 criminology students preparing for assessments.

Criminology

Biology Paper 1 Overview

Comprehensive study notes covering key concepts in cellular biology, human digestion, respiration, photosynthesis, and the circulatory system. This resource includes detailed explanations of cell structures, enzyme functions, nutrient absorption, and the impact of environmental factors on biological processes. Ideal for students preparing for Biology Paper 1 exams.

Biology

Macbeth: Guilt and Ambition

Explore the complex themes of guilt and ambition in Shakespeare's 'Macbeth'. This analysis covers key characters, including Macbeth and Lady Macbeth, their moral dilemmas, and the tragic consequences of their ambition. Ideal for students studying character motivations, thematic elements, and the psychological impact of power. Includes insights on the natural order, manipulation, and the descent into madness.

English Literature

Language Paper 1 Strategies

Master the AQA English Language Paper 1 with this comprehensive guide. Explore key strategies for language and structural analysis, critical evaluation, and creative writing. Learn how to effectively analyze texts, utilize literary techniques, and enhance your writing skills to excel in your exams.

English Language

Can't find what you're looking for? Explore other subjects.

Students love us — and so will you.

4.9/5

App Store

4.8/5

Google Play

The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.

Stefan S

iOS user

This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.

Samantha Klich

Android user

Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.

Anna

iOS user

Best app on earth! no words because it’s too good

Thomas R

iOS user

Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.

Basil

Android user

This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.

David K

iOS user

The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!

Sudenaz Ocak

Android user

In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.

Greenlight Bonnie

Android user

very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.

Rohan U

Android user

I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.

Xander S

iOS user

THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮

Elisha

iOS user

This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now

Paul T

iOS user

Stefan S

iOS user

Samantha Klich

Android user

Anna

iOS user

Best app on earth! no words because it’s too good

Thomas R

iOS user

Basil

Android user

David K

iOS user

Sudenaz Ocak

Android user

In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.

Greenlight Bonnie

Android user

Rohan U

Android user

Xander S

iOS user

Elisha

iOS user

Paul T

iOS user

Chemistry

•

155

•

25 Dec 2025

•

4 pages

Understanding Carboxylic Acids - Chapter 26.3

sheila

@study_withsheila

Carboxylic acids are everywhere around you - from the vinegar in your chips to the citric acid in your fizzy drinks. Understanding their structure and reactions is crucial for your A-level chemistry success, and once you grasp the basics, you'll... Show more

Sign up to see the contentIt's free!

Access to all documents

Improve your grades

Join milions of students

By signing up you accept Terms of Service and Privacy Policy

Carboxylic Acids - Structure and Basics

Key Insight: The -COOH group combines two familiar functional groups (carbonyl and hydroxyl), which explains why carboxylic acids are so reactive and versatile.

Sign up to see the contentIt's free!

Access to all documents

Improve your grades

Join milions of students

By signing up you accept Terms of Service and Privacy Policy

Solubility and Physical Properties

Exam Tip: Remember that melting and boiling points are unusually high for carboxylic acids due to that hydrogen bonding - this often comes up in exam questions!

Sign up to see the contentIt's free!

Access to all documents

Improve your grades

Join milions of students

By signing up you accept Terms of Service and Privacy Policy

Acid Behaviour and Reactions

The naming pattern for the salts is straightforward - just change the '-oic acid' ending to '-oate'. So ethanoic acid becomes ethanoate, propanoic acid becomes propanoate, and so on.

Memory Aid: Think of carboxylic acids as "polite acids" - they donate protons, but not too aggressively, unlike strong acids like hydrochloric acid.

Sign up to see the contentIt's free!

Access to all documents

Improve your grades

Join milions of students

By signing up you accept Terms of Service and Privacy Policy

Specific Reactions You Need to Know

Practical Note: That fizzing test with sodium carbonate is dead useful for identifying unknown compounds in your practicals - if it fizzes, you've likely got a carboxylic acid!