7 constitutional isomers of molecular formula C4H10O names structural isomers functional group 8 unique isomers structural formula skeletal formula of butanol methoxypropane ethoxyethane Doc Brown's advanced level chemistry revision notes for AQA Edexcel OCR Salters IB US honors courses

isomers of C₄H₁₀O

Advanced level organic chemistry PART 14.7: Structural isomers of molecular formula C₄H₁₀O

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Doc Brown's Advanced Chemistry: Part 14.7 Isomerism in organic chemistry

The 7 constitutional structural chain, positional and functional group isomers of molecular formula C₄H₁₀O

Sub-index for this page

Introduction to the structure and isomerism of the isomers of C₄H₁₀O

Details of the constitutional isomers and stereoisomers of molecular formula C₄H₁₀O

A comparison of the spectra of some of these isomers which can help identify them

Key revision points for the isomers of C₄H₁₀O

Practise multiple choice exam questions based on the isomers of C₄H₁₀O

Learning objectives - questions to be answered concerning the isomers of C₄H₁₀O

Associated organic chemistry page links

Index of sets of isomers for a given molecular formula

Answers to the practise multiple choice exam questions based on the isomers of C₄H₁₀O

[Author © Dr WP Brown PhD: Doc Brown's advanced level organic chemistry exam revision notes suitable for students of UK advanced level chemistry courses, IB chemistry & US K12 grade 11, grade 12 and AP honors chemistry courses: Molecular spectroscopy and analysing the isomers of C₄H₁₀O [updated RE-EDIT]

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Associated organic chemistry page links

Index of sets of isomers for a given molecular formula

This is a big chemistry website, please allow time to explore it

The 7 aliphatic non-cyclic alcohol and ether structural isomers of molecular formula C₄H₁₀O

7 constitutional isomers of C4H10O names skeletal structural formula types of isomerism how to analysise C4H10O for functional group R/S optical isomers positional substituent isomers uses applications Doc Brown's advanced level organic chemistry revision notes

Introduction to isomerism for molecular formula C₄H₁₀O (see also summary diagram)

Percent mass composition of C₄H₁₀O based on the relative atomic masses

C= 12.01 H = 1.01 O = 16.00 and M_r(C₄H₁₀O) = 74.14

Element composition of C₄H₁₀O by mass: 64.80% carbon * 13.62% hydrogen * 21.58% oxygen

Empirical formula = molecular formula = C₄H₁₀O

Structural isomerism - isomers based on different connectivity's of the constituent atoms, so cannot be spatially identical (but can be defined as having the same shape).

This includes (a) carbon chain variation (usually need a minimum of 4 atoms), (b) change in position of a substituent or functional group and (c) functional group isomerism where the atoms have a different connectivity configuration, usually with significant differences in chemical and physical properties.

All three are applicable for isomers of C₄H₁₀O

(a) carbon chain variation and variation of C-O-C chains in ethers rather than C-C-C

(b) variation of position of hydroxy/alcohol (OH) and methoxy (OCH₃) groups in the carbon chain.

(c) functional group isomerism - alcohol C-O-H group and ether C-O-C linkage

Stereoisomerism - isomers based on the same connectivity of the atoms (same constitutional formula), but in some way, they are 2D or 3D spatially different non-superimposable images (e.g. E/Z 'geometrical' isomers or mirror image R/S 'optical' isomers)

E/Z stereoisomerism was called 'geometrical isomerism' e.g. cis and trans isomers of alkenes or disubstituted cyclic alkanes where there are 3D spatial variations that are not mirror images and not super imposable.

E/Z geometrical isomerism is not possible with isomers of C₄H₁₀O

R/S stereoisomerism was called 'optical isomerism', the pairs of isomers are called enantiomers which are 3D non-superimposable mirror image forms of the molecule. The molecule must have a chiral centre (a stereocentre), that is an asymmetric carbon atom with four different atoms/groups attached to it.

There is one constitutional C₄H₁₀O isomer that can exhibit R/S optical isomerism (1 alcohol, butan-2-ol).

NOTE

C₄H₁₀O isomers are a good example of functional group isomerism: alcohol C-O-H linkage isomers versus ether C-O-C linkage isomers.

There are 7 constitutional-structural isomers of C₄H₁₀O, but 8 distinct unique isomers of C₄H₁₀O including the pair of R/S isomers (enantiomers, 'optical isomers').

Details of the 7 constitutional isomers and stereoisomers of molecular formula C₄H₁₀O

There are four isomeric alcohols and three isomeric ethers of molecular formula C₄H₁₀O

The four isomeric aliphatic alcohols

(1) butan-1-ol, 1-butanol, , , is a linear primary alcohol

Number of low resolution NMR chemical shift δ signal peaks: 5 ¹H and 4 ¹³C (email if disagree?)

¹H NMR proton ratio of integrated peak areas: 3 : 2 : 2 : 2 : 1 (for equivalent protons)

Some key wavenumbers from the infrared spectra of the isomers of C₄H₁₀O

(2) butan-2-ol, 2-butanol, , is a linear secondary alcohol

This has a chiral (asymmetric) carbon atom (2nd C2), so can also exhibit R/S stereoisomerism because a pair of two non-imposable mirror images can exist fro butan-2-ol

The R/S stereoisomers of butan-2-ol (pair of enantiomers, non-superimposable mirror images structures, optical isomers)

From the CIP assignment priority rule for R/S isomers: ₈O > ₆C₆C > ₆C₁H > ₁H

Number of low resolution NMR chemical shift δ signal peaks: 5 ¹H and 4 ¹³C (email if disagree?)

¹H NMR proton ratio of integrated peak areas: 3 : 1 : 1 : 2 : 3 (for equivalent protons)

Some key wavenumbers from the infrared spectra of the isomers of C₄H₁₀O

(3) 2-methylpropan-1-ol, 2-methyl-2-butanol, , , is a branched primary alcohol

Number of low resolution NMR chemical shift δ signal peaks: 4 ¹H and 3 ¹³C (email if disagree?)

¹H NMR proton ratio of integrated peak areas: 6 (3+3) : 1 : 2 : 1 (for equivalent protons)

Some key wavenumbers from the infrared spectra of the isomers of C₄H₁₀O

(4) 2-methylpropan-2-ol, 2-methyl-2-propanol, , , is a tertiary alcohol

Number of low resolution NMR chemical shift δ signal peaks: 2 ¹H and 2 ¹³C (email if disagree?)

¹H NMR proton ratio of integrated peak areas: 9 (3x3) : 1 (for equivalent protons)

Some key wavenumbers from the infrared spectra of the isomers of C₄H₁₀O

There are three isomeric aliphatic ethers

(5) ethoxyethane, , (ether, diethyl ether)

Number of low resolution NMR chemical shift δ signal peaks: 2 ¹H and 2 ¹³C (email if disagree?)

¹H NMR proton ratio of integrated peak areas: 6 (3+3) : 4 (2+2) (for equivalent protons)

Some key wavenumbers from the infrared spectra of the isomers of C₄H₁₀O

(6) 1-methoxypropane , (ether, methyl propyl ether)

Number of low resolution NMR chemical shift δ signal peaks: 4 ¹H and 4 ¹³C (email if disagree?)

¹H NMR proton ratio of integrated peak areas: 3 : 2 : 2 : 3 (for equivalent protons)

Some key wavenumbers from the infrared spectra of the isomers of C₄H₁₀O

(7) 2-methoxypropane , (ether, isopropyl methyl ether)

Number of low resolution NMR chemical shift δ signal peaks: 3 ¹H and 3 ¹³C (email if disagree?)

¹H NMR proton ratio of integrated peak areas: 6 : 1 : 3 (for equivalent protons)

Some key wavenumbers from the infrared spectra of the isomers of C₄H₁₀O

A comparison of the spectra of some of these isomers which can help identify them

Infrared spectra of 4 isomeric alcohols of molecular formula C₄H₁₀O

The infrared spectrum of butan-1-ol (1-butanol)

The infrared spectrum of butan-2-ol (2-butanol)

The infrared spectrum of 2-methylpropan-1-ol

The infrared spectrum of 2-methylpropan-2-ol

Mass spectra of 4 isomeric alcohols of molecular formula C₄H₁₀O

The mass spectrum of butan-1-ol (1-butanol,)

The mass spectrum of butan-2-ol (2-butanol)

The mass spectrum of 2-methylpropan-1-ol

The mass spectrum of 2-methylpropan-2-ol

1H NMR spectra of 4 isomeric alcohols of molecular formula C₄H₁₀O

The H-1 NMR spectrum of butan-1-ol (1-butanol)

The H-1 NMR spectrum of butan-2-ol (2-butanol)

The H-1 NMR spectrum of 2-methylpropan-1-ol

The H-1 NMR spectrum of 2-methylpropan-2-ol

C13 NMR spectra of 4 isomeric alcohols of molecular formula C₄H₁₀O

The C-13 NMR spectrum of butan-1-ol (1-butanol)

The C-13 NMR spectrum of butan-2-ol (2-butanol)

The C-13 NMR spectrum of 2-methylpropan-1-ol

The C-13 NMR spectrum of 2-methylpropan-2-ol

Infrared spectra of 3 isomeric ethers, molecular formula C₄H₁₀O (see 4 isomeric alcohols too)

Infrared spectrum of ethoxyethane (diethyl ether)

The infrared spectrum of 1-methoxypropane (methyl propyl ether)

The infrared spectrum of 2-methoxypropane (methyl isopropyl ether)

Mass spectra of 3 isomeric ethers, molecular formula C₄H₁₀O (see 4 isomeric alcohols too)

The mass spectrum of ethoxyethane (diethyl ether)

The mass spectrum of 1-methoxypropane (methyl propyl ether)

The mass spectrum of 2-methoxypropane (methyl isopropyl ether)

1H NMR spectra of 3 isomeric ethers of molecular formula C₄H₁₀O (see 4 isomeric alcohols too)

The H-1 NMR spectrum of Ethoxyethane (diethyl ether)

The H-1 NMR spectrum of 1-methoxypropane (methyl propyl ether)

The H-1 NMR spectrum of 2-methoxypropane (methyl isopropyl ether)

C13 NMR spectra of 3 isomeric ethers of molecular formula C₄H₁₀O (see 4 isomeric alcohols too)

The C-13 NMR spectrum of ethoxyethane

The C-13 NMR spectrum of 1-methoxypropane (methyl propyl ether)

The C-13 NMR spectrum of 2-methoxypropane (methyl isopropyl ether)

KEY REVISION POINTS for the isomers of C₄H₁₀O

Some key wavenumbers from the infrared spectra of the isomers of C₄H₁₀O

The table shows key IR absorptions for O–H, C–H, and C–O bonds.

The broad O–H stretch and fingerprint region are crucial for identification and exam analysis.

Key IR Absorption Features of C₄H₁₀O

C₄H₁₀O includes both primary alcohols (e.g. 1-butanol) and secondary alcohols (e.g. 2-butanol or isobutanol). Their IR spectra share common features:

Bond Type	Wavenumber (cm⁻¹)	Appearance	Assignment
O–H stretch (alcohol)	3200–3600	Broad, strong	Hydrogen-bonded alcohol group
C–H stretch (alkane)	2850–2960	Sharp, medium	Methyl and methylene groups
C–O stretch (alcohol)	1000–1260	Strong, sharp	Alcohol C–O single bond
O–H bend (alcohol)	1400–1440	Weak to medium	Bending vibration of hydroxyl group
CH₂ bend (alkane)	1450–1470	Medium	Methylene scissoring
CH₃ bend (alkane)	1370–1390	Medium	Methyl symmetric bending

Common misconceptions in IR spectroscopy exams for questions involving the isomers of C₄H₁₀O

Confusing O–H stretch with N–H or carboxylic acid: Alcohol O–H is broad but not as wide or intense as carboxylic acids.
Overlooking C–O stretch: Students often miss this key fingerprint region peak (1000–1260 cm⁻¹), crucial for confirming alcohols.
Assuming all broad peaks are O–H: Water contamination or overlapping peaks can mislead interpretation.
Ignoring fingerprint region: While complex, it holds vital clues for functional group confirmation.

Exam Revision Tips for IR Spectroscopy for questions involving the isomers of C₄H₁₀O

For A Level

Memorise key wavenumber ranges: Especially O–H, C=O, C–H, and C–O.
Practice spectrum matching: Identify functional groups from given spectra.
Use comparative analysis: Spot differences between alcohols, ketones, and acids.
Link to structure: Relate IR peaks to molecular formula and bonding.
Understand peak shape and intensity: Not just position—broad versus sharp, strong versus weak.
Apply to unknowns: Use IR to deduce or confirm molecular identity.
Integrate with other techniques: Combine IR with NMR or MS for full structural analysis.
Explain reasoning: Justify peak assignments in written responses.

Advanced Insight for teachers and students

Primary versus secondary alcohols: Slight shifts in O–H and C–O stretches due to hydrogen bonding differences.
Isomer differentiation: IR alone may not distinguish isomers—combine with boiling point or NMR.
Spectral overlays: Create comparative overlays for classroom use showing 1-butanol versus 2-butanol.

Summary and extra information about the isomers of C₄H₁₀O

There are seven constitutional isomers of C₄H₁₀O: four alcohols and three ethers.

Constitutional Isomers of C₄H₁₀O

Alcohols	Ethers
1-butanol, butan-1-ol	1-methoxypropane
2-butanol, butan-2-ol	2-methoxypropane
2-methyl-1-propanol, 2-methylpropan-1-ol	ethoxyethane (diethyl ether)
2-methyl-2-propanol, 2-methylpropan-2-ol

Alcohols have an –OH group bonded to a saturated carbon.
Ethers have an oxygen atom bonded to two alkyl groups (R–O–R′).

Types of Isomerism in C₄H₁₀O molecules

For C₄H₁₀O

Chain isomerism: Straight-chain versus branched-chain.
No functional group or positional isomerism, as both are alkanes.

For C₄H₁₀O:

Functional group isomerism: Alcohols versus ethers.
Chain isomerism: Straight versus branched carbon skeleton.
Positional isomerism: Location of –OH or –O– group on the chain.

Physical Property Differences the isomers of C₄H₁₀O

Property	Alcohols	Ethers
Boiling point	Higher (due to hydrogen bonding)	Lower (no hydrogen bonding)
Solubility in water	Good (especially lower primary alcohols)	Moderate to low
Volatility	Lower - H-bonding increasing intermolecular forces	Higher

Branched isomers generally have lower boiling points than straight-chain counterparts due to reduced surface area.

Chemical Reactivity and Reactions of the isomers of C₄H₁₀O

Alcohols:
- Undergo oxidation (primary → aldehyde → carboxylic acid; secondary → ketone).
- Dehydration to form alkenes.
- Esterification with carboxylic acids.
Ethers:
- Relatively inert.
- Cleaved by strong acids (e.g., HI, HBr).

Reactivity order (alcohols):

Primary > Secondary > Tertiary for oxidation;

Tertiary > Secondary > Primary for acid-catalyzed dehydration.

Uses and Applications of the isomers of C₄H₁₀O

1-butanol: Solvent, precursor in perfumes and plastics.
2-butanol: Industrial solvent.
2-methyl-2-propanol (tert-butanol): Fuel additive, lab reagent.
Diethyl ether: Historical anaesthetic, solvent in Grignard reactions.

Common Student Misconceptions about the isomers of C₄H₁₀O

Confusing constitutional isomers with stereoisomers.
Assuming all alcohols behave the same chemically.
Forgetting that ethers lack hydrogen bonding, affecting boiling points.
Misidentifying oxidation products of alcohols.

Exam Revision Tips for questions involving the isomers of C₄H₁₀O

Draw all isomers systematically: start with straight chains, then branch.
Practice naming using IUPAC rules—watch for position numbers.
Compare boiling points and solubility based on structure and bonding.
Use oxidation flowcharts for alcohol reactions.
Link structure to reactivity: tertiary alcohols resist oxidation but dehydrate easily.
Use past papers to identify common question styles (e.g., “Explain why…” or “Draw and name…”).
For AP/IB: Emphasize mechanisms and reaction conditions.

Practise multiple choice exam questions based on the isomers of C4H10O

You may have to sketch out some molecular structures to work out the answer.

If you think there is an error email me asap chem55555@hotmail.com

A Co-Pilot AI experiment: Here’s a focused set of 12 exam-style multiple-choice questions on the constitutional isomers (alcohols and ethers), with detailed feedback, distractor explanations, and common misconceptions.

The relevant IUPAC isomers are:

Alcohols: butan-1-ol, butan-2-ol, 2-methylpropan-1-ol, 2-methylpropan-2-ol
Ethers: 1-methoxypropane, 2-methoxypropane, ethoxyethane
You may have to sketch out some molecular structures to work out the answer.

If you think there is an error email me asap chem55555@hotmail.com

Q1. Number of alcohol and ether isomers

How many distinct alcohol and ether constitutional isomers with molecular formula C(4)H({10})O are there in total?

A. 5
B. 7
C. 8
D. 9

Q2. Primary versus secondary versus tertiary alcohols

Which of the following is a tertiary alcohol?

A. butan-1-ol
B. butan-2-ol
C. 2-methylpropan-1-ol
D. 2-methylpropan-2-ol

Q3. IR spectroscopy: identifying an alcohol

Which isomer would show a broad O–H stretching absorption around 3200–3600 cm(^{-1}) in its IR spectrum?

A. butan-1-ol
B. 1-methoxypropane
C. ethoxyethane
D. 2-methoxypropane

Q4. ¹H NMR: number of distinct proton environments

Which isomer is expected to show the greatest number of distinct proton environments in its (^1)H NMR spectrum?

A. 2-methylpropan-2-ol
B. ethoxyethane
C. butan-2-ol
D. 2-methoxypropane

Q5. Oxidation behaviour of alcohol isomers

Which alcohol cannot be oxidised (under normal conditions with acidified dichromate) to a carbonyl compound?

A. butan-1-ol
B. 2-methylpropan-2-ol
C. butan-2-ol
D. 2-methylpropan-1-ol

Q6. ¹³C NMR: number of carbon environments

Which isomer would show only two distinct carbon environments in its ¹³C NMR spectrum?

A. butan-1-ol
B. butan-2-ol
C. 1-methoxypropane
D. 2-methylpropan-2-ol

Q7. Distinguishing an ether from an alcohol by simple tests

Which statement correctly describes a simple way to distinguish ethoxyethane from butan-1-ol in the lab?

A. Ethoxyethane will react with acidified potassium dichromate(VI), turning the solution green.
B. Butan-1-ol will not burn in air, whereas ethoxyethane will burn readily.
C. Butan-1-ol will react with sodium metal to produce hydrogen gas, whereas ethoxyethane will not.
D. Ethoxyethane will give a positive test with Tollens’ reagent, whereas butan-1-ol will not.

Q8. ¹H NMR: presence of an OH proton

Which isomer’s ¹H NMR spectrum would typically show a broad, exchangeable signal (often around 1–5 ppm) that disappears on adding D₂O to the specimen, indicating an OH proton?

A. 2-methylpropan-1-ol
B. ethoxyethane
C. 1-methoxypropane
D. 2-methoxypropane

Q9. Boiling point comparison

Which compound is expected to have the highest boiling point?

A. 1-methoxypropane
B. ethoxyethane
C. 2-methoxypropane
D. butan-1-ol

Q10. Dehydration to an alkene

Which alcohol is most likely to give 2-methylpropene as the major product on dehydration with hot concentrated sulfuric acid?

A. butan-1-ol
B. 2-methylpropan-2-ol
C. 2-methylpropan-1-ol
D. butan-2-ol

Q11. Distinguishing butan-1-ol and butan-2-ol by oxidation

Which statement correctly describes a way to distinguish butan-1-ol from butan-2-ol using acidified potassium dichromate(VI)?

A. Neither will change the colour of acidified dichromate(VI).
B. Both will change the colour of acidified dichromate(VI), but only butan-1-ol forms a ketone.
C. Both will change the colour of acidified dichromate(VI), but butan-1-ol can be further oxidised to a carboxylic acid.
D. Only butan-2-ol will change the colour of acidified dichromate(VI).

Q12. ¹H NMR splitting pattern clue

A compound with formula C₄H₁₀O shows a ¹H NMR spectrum containing only one sharp singlet (ignoring the OH proton). Which isomer is most consistent with this data?

A. 2-methylpropan-2-ol
B. butan-1-ol
C. ethoxyethane
D. 1-methoxypropane

You may have to sketch out some molecular structures to work out the answer.

If you think there is an error email me asap chem55555@hotmail.com

Learning objectives - questions to be answered concerning the isomers of C₄H₁₀O

How many constitutional isomers are there of formula C4H10O?

How do you draw the skeletal structure of isomers of C4H10O?

How do you draw the structural formula of isomers of C4H10O?

Can you recognise the different functional groups in the isomers of C4H10O?

How do you name the isomers of C4H10O?

How do you work out the structure of the isomers of molecular formula C4H10O?

How do you draw the structural formula and skeletal formula of the isomers of molecular formula C4H10O?

How do you name the isomers of molecular formula C4H10O?

How many aliphatic structural isomers are there of molecular formula C4H10O?

How many aliphatic carbon chain isomers are there of molecular formula C4H10O?

How many positional isomers are there of molecular formula C4H10O?

How many E/Z (geometrical) isomers are there of molecular formula C4H10O?

How many R/S (optical) isomers (enantiomers) of molecular formula C4H10O?

Are there any functional group isomers with a molecular formula C4H10O?

Does C4H10O have any stereoisomers?

Be able to work out the number of different 1H proton NMR chemical shift signals for C4H10O isomers

Be able to work out the number of different 13C NMR chemical shift signals for C4H10O isomers

This page will answer these questions for molecular formulae C₄H₁₀O

Associated organic chemistry links

Advanced Level pre-university organic chemistry notes

IR, mass and H-1 & C-13 NMR spectra of organic compounds

Index of sets of isomers for a given molecular formula

The molecular structure and naming of aliphatic ALCOHOLS including isomeric ethers

INDEX of ALL revision notes on the chemistry of ALCOHOLS (and mention of ethers)

For isomerism in organic chemistry, see also the notes

Isomerism: introduction, structural isomerism - chain, positional, functional group, tautomerism

Stereoisomerism: introduction, definition, priority rules, E/Z isomerism (cis/trans isomerism)

Stereoisomerism - R/S isomerism (optical isomerism) - definition - examples explained

This is a big chemistry website, please allow time to explore it

Index of advanced (pre-university) organic chemistry revision notes

The chemistry of alkanes and the petrochemical industry

The chemistry of alkenes

The chemistry of organic halogen compounds

The chemistry of alcohols

The chemistry of aldehydes and ketones

The chemistry of carboxylic acids and derivatives

The chemistry of organo-nitrogen compounds

The chemistry of aromatic compounds

A summary chart of isomerism

ANSWERS to the practise multiple choice exam questions

You may have to sketch out some molecular structures to work out the answer.

If you think there is an error email me asap chem55555@hotmail.com

Q1. Number of alcohol and ether isomers

How many distinct alcohol and ether constitutional isomers with molecular formula C(4)H({10})O are there in total?

A. 5
B. 7
C. 8
D. 9

Correct answer: B

Explanation:

There are 4 alcohols: butan-1-ol, butan-2-ol, 2-methylpropan-1-ol, 2-methylpropan-2-ol.
There are 3 ethers: 1-methoxypropane, 2-methoxypropane, ethoxyethane.
Total = (4 + 3 = 7).

Why the distractors are wrong:

A (5): Underestimates—ignores branching and ether isomers.
C (8) and D (9): Overcount—often from double-counting positional isomers or inventing impossible structures.

Tip / misconception:
Students often forget that ethers can also be constitutional isomers of alcohols with the same formula. Always consider both functional groups when given only a molecular formula.

Q2. Primary versus secondary versus tertiary alcohols

Which of the following is a tertiary alcohol?

A. butan-1-ol
B. butan-2-ol
C. 2-methylpropan-1-ol
D. 2-methylpropan-2-ol

Correct answer: D

Explanation:

In 2-methylpropan-2-ol, the carbon bearing the OH group is attached to three other carbons → tertiary.

Why the distractors are wrong:

A (butan-1-ol): OH on a carbon attached to only one other carbon → primary.
B (butan-2-ol): OH on a carbon attached to two other carbons → secondary.
C (2-methylpropan-1-ol): OH on a carbon attached to one other carbon → primary.

Tip / misconception:
Don’t classify primary/secondary/tertiary by “how substituted the OH looks”; it’s about how many carbon atoms are directly bonded to the carbon bearing the OH, not to the oxygen.

Q3. IR spectroscopy: identifying an alcohol

Which isomer would show a broad O–H stretching absorption around 3200–3600 cm(^{-1}) in its IR spectrum?

A. butan-1-ol
B. 1-methoxypropane
C. ethoxyethane
D. 2-methoxypropane

Correct answer: A

Explanation:

Alcohols show a broad O–H stretch in the 3200–3600 cm^-1 region.
butan-1-ol is an alcohol, so it shows this broad band.

Why the distractors are wrong:

B, C, D: All are ethers; ethers lack an O–H bond and therefore do not show the broad O–H stretch, only C–O stretches around 1000–1200 cm^-1.

Tip / misconception:
Students sometimes think “any oxygen-containing compound” shows an O–H peak. Only compounds with an actual O–H bond (alcohols, carboxylic acids, etc.) show that broad O–H stretch.

Q4. ¹H NMR: number of distinct proton environments

Which isomer is expected to show the greatest number of distinct proton environments in its (^1)H NMR spectrum?

A. 2-methylpropan-2-ol
B. ethoxyethane
C. butan-2-ol
D. 2-methoxypropane

Correct answer: C

Explanation (qualitative):

butan-2-ol is relatively unsymmetrical: it has an OH-bearing CH, two different CH₃ groups (on each side), and a CH₂ group, plus the OH proton → several distinct environments.
The others have more symmetry or equivalent groups, reducing the number of distinct signals.

Why the distractors are wrong (qualitative reasoning):

A (2-methylpropan-2-ol): Highly symmetrical; three equivalent CH₃ groups plus OH → fewer signals.
B (ethoxyethane): Symmetrical ether (diethyl ether); both ethyl groups are equivalent.
D (2-methoxypropane): Has equivalent methyl groups attached to the same carbon, reducing the number of distinct environments.

Tip / misconception:
Students often count “types of groups” CH₃, CH₂, CH) instead of unique environments. Always consider symmetry—equivalent groups give one signal.

Q5. Oxidation behaviour of alcohol isomers

Which alcohol cannot be oxidised (under normal conditions with acidified dichromate) to a carbonyl compound?

A. butan-1-ol
B. 2-methylpropan-2-ol
C. butan-2-ol
D. 2-methylpropan-1-ol

Correct answer: B

Explanation:

Tertiary alcohols (like 2-methylpropan-2-ol) lack a hydrogen on the carbon bearing the OH group, so they are resistant to oxidation to carbonyl compounds under typical conditions.

Why the distractors are wrong:

A (butan-1-ol): Primary alcohol → oxidised to aldehyde and then carboxylic acid.
C (butan-2-ol): Secondary alcohol → oxidised to a ketone.
D (2-methylpropan-1-ol): Primary alcohol → oxidised to aldehyde and then carboxylic acid.

Tip / misconception:
A common error is to assume “all alcohols oxidise”. Check for a hydrogen on the carbon bearing the OH—no such hydrogen means no simple oxidation to a carbonyl.

Q6. ¹³C NMR: number of carbon environments

Which isomer would show only two distinct carbon environments in its ¹³C NMR spectrum?

A. butan-1-ol
B. butan-2-ol
C. 1-methoxypropane
D. 2-methylpropan-2-ol

Correct answer: D

Explanation:

2-methylpropan-2-ol has:
- One quaternary carbon (attached to OH and three CH(_3) groups).
- Three equivalent CH(_3) groups (all identical).
  So only two distinct carbon environments.

Why the distractors are wrong (qualitative):

A, B, C: Each has more than two distinct carbon environments because of less symmetry and different positions relative to the functional group.

Tip / misconception:
Students often forget that multiple identical groups (like three equivalent CH₃ groups) give one signal, not three. Symmetry drastically reduces the number of ¹³C signals.

Q7. Distinguishing an ether from an alcohol by simple tests

Which statement correctly describes a simple way to distinguish ethoxyethane from butan-1-ol in the lab?

Correct answer: C

Explanation:

Alcohols (like butan-1-ol) react with sodium metal to form a salt and hydrogen gas.
Ethers (like ethoxyethane) do not react with sodium metal under these conditions.

Why the distractors are wrong:

A: Ethoxyethane (an ether) is not oxidised by acidified dichromate; butan-1-ol (a primary alcohol) is.
B: Both are flammable and will burn in air.
D: Tollens’ reagent tests for aldehydes, not for alcohols or ethers.

Tip / misconception:
Students sometimes think “any oxygen-containing compound” reacts with sodium or oxidising agents. Reaction patterns depend on functional group, not just the presence of oxygen.

Q8. ¹H NMR: presence of an OH proton

Which isomer’s ¹H NMR spectrum would typically show a broad, exchangeable signal (often around 1–5 ppm) that disappears on adding D₂O to the specimen, indicating an OH proton?

A. 2-methylpropan-1-ol
B. ethoxyethane
C. 1-methoxypropane
D. 2-methoxypropane

Correct answer: A

Explanation:

2-methylpropan-1-ol is an alcohol and contains an OH proton, which appears as a broad signal and disappears on D(_2)O exchange.

Why the distractors are wrong:

B, C, D: All ethers; they have no OH proton, so no such broad, exchangeable signal.

Tip / misconception:
Students sometimes misinterpret broad signals as “impurities”. In alcohols, a broad, exchangeable peak is a key diagnostic feature for the OH proton.

Q9. Boiling point comparison

Which compound is expected to have the highest boiling point?

A. 1-methoxypropane
B. ethoxyethane
C. 2-methoxypropane
D. butan-1-ol

Correct answer: D

Explanation:

butan-1-ol can form strong hydrogen bonds between molecules due to the OH group, leading to a significantly higher boiling point than the ethers, which can only form dipole–dipole and London dispersion forces.

Why the distractors are wrong:

A, B, C (ethers): No O–H bond → no hydrogen bonding between molecules → lower boiling points compared with an alcohol of similar molar mass.

Tip / misconception:
Students often overemphasise “molecular mass” and forget intermolecular forces. Hydrogen bonding usually dominates boiling point trends among molecules of similar size.

Q10. Dehydration to an alkene

Which alcohol is most likely to give 2-methylpropene as the major product on dehydration with hot concentrated sulfuric acid?

A. butan-1-ol
B. 2-methylpropan-2-ol
C. 2-methylpropan-1-ol
D. butan-2-ol

Correct answer: B

Explanation:

2-methylpropan-2-ol (a tertiary alcohol) dehydrates to give the more substituted alkene 2-methylpropene.
Tertiary alcohols dehydrate readily and often follow Zaitsev’s rule (more substituted alkene favoured).

Why the distractors are wrong:

A (butan-1-ol): Dehydration gives mainly but-1-ene and but-2-ene, not 2-methylpropene.
C (2-methylpropan-1-ol): Dehydration would give mainly 2-methylprop-1-ene (less substituted) or rearranged products under harsher conditions, but not straightforwardly 2-methylpropene as the major product at this level.
D (butan-2-ol): Dehydration gives mainly but-2-ene.

Tip / misconception:
Students sometimes ignore carbocation stability and Zaitsev’s rule. More substituted alkenes are usually more stable and therefore favoured in dehydration of alcohols.

Q11. Distinguishing butan-1-ol and butan-2-ol by oxidation

Which statement correctly describes a way to distinguish butan-1-ol from butan-2-ol using acidified potassium dichromate(VI)?

Correct answer: C

Explanation:

Both primary (butan-1-ol) and secondary (butan-2-ol) alcohols are oxidised by acidified dichromate(VI), turning the solution from orange to green.
butan-1-ol can be oxidised first to butanal and then to butanoic acid.
butan-2-ol is oxidised to butan-2-one (a ketone), which is not further oxidised under these conditions.

Why the distractors are wrong:

A: Incorrect—both are oxidised.
B: Butan-1-ol forms an aldehyde (and then an acid), not a ketone.
D: Both, not just butan-2-ol, cause the colour change.

Tip / misconception:
Students often think “primary → aldehyde only” and forget further oxidation to carboxylic acid, or they confuse which type gives ketones (secondary).

Q12. ¹H NMR splitting pattern clue

A compound with formula C₄H₁₀O shows a ¹H NMR spectrum containing only one sharp singlet (ignoring the OH proton). Which isomer is most consistent with this data?

A. 2-methylpropan-2-ol
B. butan-1-ol
C. ethoxyethane
D. 1-methoxypropane

Correct answer: A

Explanation:

2-methylpropan-2-ol has three equivalent CH(_3) groups attached to the same carbon, and they are not adjacent to any other non-equivalent protons (apart from the OH, which often appears separately and may be broad).
All nine protons of the three CH₃ groups are equivalent and see no neighbouring non-equivalent protons → one sharp singlet.

Why the distractors are wrong (qualitative):

B (butan-1-ol): Has multiple environments and splitting patterns.
C (ethoxyethane): Has at least two signals with splitting.
D (1-methoxypropane): Has different CH₃ groups (on O and on carbon chain) → multiple signals.

Tip / misconception:
Students often forget that equivalent groups give a single signal and that lack of neighbouring non-equivalent protons gives a singlet. Highly symmetrical structures often give very simple NMR spectra.

You may have to sketch out some molecular structures to work out the answer.

If you think there is an error email me asap chem55555@hotmail.com

Website content © Dr Phil Brown 2000+. All copyrights reserved on revision notes, images, quizzes, worksheets etc. Copying of Doc Brown's pre-university advanced level chemistry website material is NOT permitted. Exam revision summaries & references to science course specifications are unofficial. These organic chemistry revision notes on the isomers of C₄H₁₀O with names, structures, types of isomerism and a few spectroscopy details are suitable for use of pre-university students studying AQA advanced level chemistry, Edexcel advanced level chemistry, OCR advanced level chemistry, IB advanced level chemistry, WJEC (Eduqas) advanced level chemistry, CIE advanced level chemistry, CCEA advanced level chemistry, US grade 11-12 AP honors chemistry courses and they will also prove useful to 1st year undergraduate students of chemistry.

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Key IR Absorption Features of C4H10O

Common misconceptions in IR spectroscopy exams for questions involving the isomers of C4H10O

Exam Revision Tips for IR Spectroscopy for questions involving the isomers of C4H10O

For A Level

Advanced Insight for teachers and students

Constitutional Isomers of C4H10O

Types of Isomerism in C4H10O molecules

For C4H10O

For C4H10O:

Physical Property Differences the isomers of C4H10O

Chemical Reactivity and Reactions of the isomers of C4H10O

Uses and Applications of the isomers of C4H10O

Common Student Misconceptions about the isomers of C4H10O

Exam Revision Tips for questions involving the isomers of C4H10O

Q1. Number of alcohol and ether isomers

Q2. Primary versus secondary versus tertiary alcohols

Q3. IR spectroscopy: identifying an alcohol

Q4. 1H NMR: number of distinct proton environments

Q5. Oxidation behaviour of alcohol isomers

Q6. 13C NMR: number of carbon environments

Q7. Distinguishing an ether from an alcohol by simple tests

Q8. 1H NMR: presence of an OH proton

Q9. Boiling point comparison

Q10. Dehydration to an alkene

Q11. Distinguishing butan-1-ol and butan-2-ol by oxidation

Q12. 1H NMR splitting pattern clue

Q1. Number of alcohol and ether isomers

Q2. Primary versus secondary versus tertiary alcohols

Q3. IR spectroscopy: identifying an alcohol

Q4. 1H NMR: number of distinct proton environments

Q5. Oxidation behaviour of alcohol isomers

Q6. 13C NMR: number of carbon environments

Q7. Distinguishing an ether from an alcohol by simple tests

Q8. 1H NMR: presence of an OH proton

Q9. Boiling point comparison

Q10. Dehydration to an alkene

Q11. Distinguishing butan-1-ol and butan-2-ol by oxidation

Q12. 1H NMR splitting pattern clue

Key IR Absorption Features of C₄H₁₀O

Common misconceptions in IR spectroscopy exams for questions involving the isomers of C₄H₁₀O

Exam Revision Tips for IR Spectroscopy for questions involving the isomers of C₄H₁₀O

Constitutional Isomers of C₄H₁₀O

Types of Isomerism in C₄H₁₀O molecules

For C₄H₁₀O

For C₄H₁₀O:

Physical Property Differences the isomers of C₄H₁₀O

Chemical Reactivity and Reactions of the isomers of C₄H₁₀O

Uses and Applications of the isomers of C₄H₁₀O

Common Student Misconceptions about the isomers of C₄H₁₀O

Exam Revision Tips for questions involving the isomers of C₄H₁₀O

Q4. ¹H NMR: number of distinct proton environments

Q6. ¹³C NMR: number of carbon environments

Q8. ¹H NMR: presence of an OH proton

Q12. ¹H NMR splitting pattern clue

Q4. ¹H NMR: number of distinct proton environments

Q6. ¹³C NMR: number of carbon environments

Q8. ¹H NMR: presence of an OH proton

Q12. ¹H NMR splitting pattern clue