|
Interpreting the
1H NMR spectrum of 1-bromopropane
[Autho r
©
Dr
Phil Brown PhD:
Doc Brown's advanced level organic chemistry exam revision notes
suitable for students of UK A level chemistry courses,
IB chemistry & US K12 grade
11, grade 12 and AP honors chemistry courses: Molecular
spectroscopy - analysing the 1H NMR spectrum of 1-bromopropane
[updated
Mar 11th 2026 *]
*
email doc
brown * [privacy policy,
cookies & disclaimer] *
Re-edit
1H NMR spectrum of
CH3CH2CH2Br
*
LINKS associated
with 1-bromopropane
*
The
chemistry of organic halogen compounds
*
This is a BIG
website, you need to take time to explore it
*
H-1 proton NMR spectroscopy -
spectra index
See also the
Isomers of molecular formula
C3H7X (where
X =
F, Cl, Br or I)
Introductory note on the 1H NMR spectra of 1-bromopropane
Students and teachers please note my explanation of the
proton NMR spectrum of 1-bromopropane is designed for advanced, but
pre-university, chemistry courses.
The chemical shift
δ splitting pattern effects for
1-bromopropane are
confined to a proton spin-spin
coupling effects analysed using the n+1 rule for adjacent
non-equivalent proton fields (n is the number of neighbouring
protons in a non-equivalent different chemical environment for the
1-bromopropane molecule).
It is assumed that the integrated intensities of the
δ
chemical shifts give the ratio of the protons in the different
non-equivalent chemical environments of the 1-bromopropane molecule.
The most common solvent used for investigating the 1H NMR
spectrum of compounds like 1-bromopropane, is CDCl3 and other
deuterated solvents to avoid confusion with a 1H NMR
signal, 2D (2H) has a different chemical
shift.
TMS is the acronym for tetramethylsilane, formula Si(CH3)4,
whose protons are arbitrarily given a chemical shift of 0.0 ppm.
This is the 'standard' in 1H NMR spectroscopy and all
other proton resonances, called chemical shifts, are measured
with respect to the TMS, and depend on the
individual (electronic) chemical environment of the hydrogen atoms
in an organic molecule - 1-bromopropane here.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of 1-bromopropane represent the peaks of the intensity of
the chemical shifts of (which are often groups of split lines at
high resolution) AND the relative integrated areas under the peaks
gives you the ratio of protons in the different chemical
environments of the 1-bromopropane molecule.
1-bromopropane,
C3H7Br,
CH3CH2CH2Br,
,
The molecular structure and naming of haloalkanes
Interpreting the
H-1 NMR spectrum of 1-bromopropane
In terms of spin-spin coupling from the possible proton magnetic orientations,
for 1-bromopropane I
have only considered the interactions of
non-equivalent protons on adjacent carbon atoms
e.g. -CH2-CH3
or >CH-CH3
or R-CH2-CH2-X
protons etc.
For relatively simple molecules, the
low
resolution H-1 NMR spectrum of 1-bromopropane is a good starting point
and would show 3 resonances in the ratio 3:2:2.
The hydrogen atoms (protons) of 1-bromopropane occupy
3
different chemical environments so that the low resolution NMR
spectra should show 3 principal peaks of different H-1 NMR chemical shifts,
all split by neighbouring protons (diagram above for
1-bromopropane).
CH3CH2CH2Br
Note the proton ratio 3:2:2 of the 3 colours of the protons
in the 3 chemically different environments
Chemical shifts
(a) to (c) on the H-1 NMR
spectrum diagram for 1-bromopropane.
Although there are 7 hydrogen atoms in the molecule,
there are only 3 possible different chemical
environments for the hydrogen atoms in 1-bromopropane molecule.
The integrated signal proton ratio 3:2:2 observed
in the high resolution H-1 NMR spectrum, corresponds with
the structural formula of 1-bromopropane.
The high resolution 1H NMR
spectrum of 1-bromopropane
The ppm quoted on the diagram represent the peak
of resonance intensity for a particular proton group in the
molecule of 1-bromopropane - since the peak' is at the apex of a band of
H-1 NMR resonances due to spin - spin coupling field splitting effects - see high resolution
notes on 1-bromopropane below.
So, using the chemical shifts and applying the
n+1 rule to
1-bromopropane
and make some predictions using some colour coding! (In problem
solving you work the other way round!)
(a)
1H
Chemical shift 1.03 ppm, methyl protons:
CH3CH2CH2Br
This resonance is split into a 1:2:1
triplet by the neighbouring CH2 protons (n+1
= 3).
Evidence for the presence of a CH2 group
in the molecule of 1-bromopropane
(b)
1H
Chemical shift 1.87 ppm, CH2 protons:
CH3CH2CH2Br
This resonance is split into a
1:5:10:10:5:1 sextet by the neighbouring CH3
and CH2 protons (n+1 = 6).
Evidence for the presence of a CH3-C-CH2 grouping
in the molecule of 1-bromopropane
(c)
1H
Chemical shift 3.39 ppm, CH2 protons:
CH3CH2CH2Br
This resonance is split into a 1:2:1
triplet by the neighbouring CH2 protons.
Evidence for the presence of a CH2 group
in the molecule of 1-bromopropane
Evidence for the presence of a 2nd CH2 group
in the molecule of 1-bromopropane, with a different
chemical shift than (b).
Note the decreasing effect on the chemical shift as the
hydrogen atom is further from the more electronegative bromine atom of 1-bromopropane.
Summary of the
H-1 NMR spectrum of 1-bromopropane and extra comments
The ¹H NMR spectrum of 1-bromopropane (CH3CH2CH2Br)
with precision, clarity, and exam-ready structure.
Overview of Proton Environments in
1-Bromopropane
1-bromopropane contains three distinct proton
environments:
- CH3 group at the end of the chain
- Middle CH2 group
- CH2 group adjacent to Br
Each gives rise to a separate signal in the spectrum due to
differing chemical environments.
Table of Chemical Shifts, Origins, and
Proton Ratios for the 1H NMR spectrum of 1-bromopropane
|
Chemical Shift (δ, ppm) |
Proton Type |
Environment |
Splitting Pattern |
Integration Ratio |
| ~0.9–1.0, 1.03 ppm |
CH3 |
Terminal methyl group |
Triplet (CH3
neighbour) |
3 |
| ~1.6–1.9, 1.87 ppm |
CH2 |
Central methylene |
Sextet (CH2 + CH2Br) |
2 |
| ~3.3–3.4, 3.39 ppm |
CH2 |
Adjacent to Br (deshielded) |
Triplet (CH2
neighbour) |
2 |
Note: Exact chemical shifts may vary slightly depending on
solvent and instrument, but the relative positions and patterns
remain consistent.
Common Misconceptions for the 1H NMR
spectrum of 1-bromopropane
(see also below)
- Misidentifying the CH2Br signal:
Students often expect it to appear further downfield (e.g. >4 ppm),
but alkyl bromides typically show CH2Br around 3.3–3.4
ppm.
- Overlooking the sextet: The central CH2
group is split by five neighboring protons (two on
CH2Br and three on CH2), giving a
sextet — often misinterpreted as a quartet or multiple
split.
- Assuming OH-like broad signals: No OH group is
present, so all signals should be sharp and well-defined.
Exam Tips for questions involving the
1H NMR spectrum of 1-bromopropane
(see also above)
- Use integration ratios to confirm the number of
protons in each environment — 3:2:2 is diagnostic for
1-bromopropane.
- Apply the n+1 rule carefully: Count neighboring
protons to predict splitting patterns.
- Recognize deshielding effects: Electronegative
atoms like Br shift nearby protons downfield (increase in chemical
shift).
- Compare with isomers: 2-bromopropane shows only
two signals due to symmetry — a useful contrast in
multiple-choice questions.
- Sketch the molecule: Annotate proton
environments and neighbours to avoid misassignments.
The splitting pattern from proton
spin-spin coupling effects is analysed using the n+1 rule for
adjacent non-equivalent proton fields (n is the number of
neighbouring protons in a non-equivalent different chemical
environment).
|
Number of directly adjacent protons 1H
causing splitting |
Splitting pattern produced from the
n+1 rule on spin-spin coupling and the theoretical ratio of line intensities |
|
0
means no splitting |
|
|
|
|
|
|
1 |
|
|
|
|
|
|
|
1
creates a doublet |
|
|
|
|
|
1 |
|
1 |
|
|
|
|
|
|
2
creates a triplet |
|
|
|
|
1 |
|
2 |
|
1 |
|
|
|
|
|
3
creates a quartet |
|
|
|
1 |
|
3 |
|
3 |
|
1 |
|
|
|
|
4
creates a quintet |
|
|
1 |
|
4 |
|
6 |
|
4 |
|
1 |
|
|
|
5
creates a sextet |
|
1 |
|
5 |
|
10 |
|
10 |
|
5 |
|
1 |
|
|
6
creates a septet |
1 |
|
6 |
|
15 |
|
20 |
|
15 |
|
6 |
|
1 |
Key words & phrases:
C3H7Br
CH3CH2CH2Br Interpreting the proton H-1 NMR spectra of 1-bromopropane, low resolution & high resolution proton
nmr spectra of 1-bromopropane, H-1 nmr spectrum of 1-bromopropane, understanding the
hydrogen-1 nmr spectrum of 1-bromopropane, explaining the line splitting patterns from
spin-spin coupling in the
high resolution H-1 nmr spectra of 1-bromopropane, revising the H-1 nmr spectrum of
1-bromopropane,
proton nmr of 1-bromopropane, ppm chemical shifts of the H-1 nmr spectrum of
1-bromopropane,
explaining and analyzing spin line splitting in the H-1 nmr spectrum, how
to construct the diagram of the H-1 nmr spectrum of 1-bromopropane, how to work out the
number of chemically different protons in the structure of the 1-bromopropane organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of 1-bromopropane using the n+1 rule to explain the spin - spin coupling
splitting in the proton nmr spectrum of 1-bromopropane deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of 1-bromopropane
examining the 1H nmr spectrum of 1-bromopropane analysing the 1-H nmr spectrum of
1-bromopropane how do you sketch and interpret the H-1 NMR spectrum of
1-bromopropane
interpreting interpretation of the 1H proton spin-spin coupling causing line
splitting in the NMR spectrum of 1-bromopropane
assignment of chemical shifts in the
proton 1H NMR spectrum of 1-bromopropane formula explaining spin-spin coupling for line splitting
of n-propyl bromide How do you interpret the H-1 NMR spectrum of 1-bromopropane How to interpret
the H-1 NMR spectrum of 1-bromopropane Explanatory diagram of the chemical
shifts of the 1H H-1 proton NMR spectrum of the 1-bromopropane
molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the
proton NMR spectrum of 1-bromopropane. How to explain the H-1 NMR spectrum of
1-bromopropane. The chemical shifts and integrated values of the proton ratios in the 1-H NMR
spectrum of the 1-bromopropane molecule. How to work out the molecular
structure of the 1-bromopropane molecule from its proton NMR spectrum. The uses
and distinctive features of the proton NMR spectrum of the
1-bromopropane
molecule explained. What does the H-1 proton NMR spectrum chemical
shifts tell us about the
structure and properties of the 1-bromopropane
molecule?
Links associated
with
1-bromopropane
The infrared spectrum of
1-bromopropane
The mass spectrum of
1-bromopropane
(propyl bromide)
The C-13 NMR spectrum of 1-bromopropane
The chemistry of HALOGENOALKANES (haloalkanes)
revision notes INDEX
H-1 proton NMR spectroscopy index
(Please
read 8 points at the top of the 1H NMR index page)
ALL SPECTROSCOPY INDEXES
All Advanced Organic
Chemistry Notes
Use My Google search site box
Email doc b:
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
spectroscopy (on the 1H NMR spectrum of 1-bromopropane) 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. |
