As the number of carbon atoms in the carboxylic acid chain increases, boiling point

Q: How does number of carbon atoms affect boiling point?

Physical properties The boiling points of alkanes increase with increasing number of carbons. This is because the intermolecular attractive forces, although individually weak, become cumulatively more significant as the number of atoms and electrons in the molecule increases.

Q: Does carboxylic acid increase boiling point?

Carboxylic acids have high boiling points compared to other substances of comparable molar mass. Boiling points increase with molar mass.

Q: What is the cause for the high boiling points of the carboxylic acids?

In a pure carboxylic acid, hydrogen bonding can occur between two molecules of acid to produce a dimer. This immediately doubles the size of the molecule and so increases the van der Waals dispersion forces between one of these dimers and its neighbors - resulting in a high boiling point.

Q: Why does boiling point increase with carbon chain length?

Melting and Boiling Point As the carbon chain gets longer, there are more electrons in a molecule. This means that there are more (relatively) stronger intermolecular forces between the molecules. As a result, it takes more energy to break these forces, and thus the melting or boiling points increase.

The tables and figures below show how the boiling point changes with increasing carbon number up to C33 for different kinds of hydrocarbons, alcohols and carboxylic acids. More detailed definitions and examples of molecular structures of the different groups are given below the figures.

Table of Contents Show

How does number of carbon atoms affect boiling point?
Does carboxylic acid increase boiling point?
What is the cause for the high boiling points of the carboxylic acids?
Why does boiling point increase with carbon chain length?

Melting point - the temperature at which a solid turns into a liquid
Boiling point - the temperature at which a liquid turns into a gas

For hydrocarbons with the same carbon number the boiling point increases in the following order:

multisubstituted alkane < singelsubstituted alkane < singelsubstituted alkene < normal alkene < normal alkane < alkyl cyclohexane < alkylbenzene < cycloalkene < cycloalkane < 2-, 4- and 3-alkanol / 1-alkylnaphthalene < 1-alkanol < normal alkanoic acid

See also pKa values for phenols, alcohols and carboxylic acids.

For full table - rotate the screen!

Boiling point of hydrocarbons, alcohols and acids, C1-C16°C
Carbon number	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16
2,2-dimetylalkane					10	50	79	106	133	155
2-methylalkane				-12	28	60	90	117	143	167	189	211
2-methylalkene				-7	31	62	92	118	145	167
3-methylalkane						63	92	120	144	168	192	212
1-alkene		-104	-48	-6	30	64	94	121	147	172	193	213	233	251
N-alkane	-162	-89	-42	-1	36	69	98	126	151	174	196	216	235	254	270	287
1-alkyne		-84	-23	8	40	71	100	126	151	174	196	215	234			284
Alkylcyclohexane*							101	132	156	178	204	225	244	263
Alkylcyclopentane						72	104	131	156	180	206	224	242	262	279
Alkylbenzene*						80	111	136	159	183	205	226	242	263
Cycloalkene**			-36	2	44	83	115
Cycloalkane**			-33	13	49	81	119	151	173	202
2-alkanol			82	99	119	138	159	179	194	212	231	249
4-alkanol							161	176	193	214
3-alkanol					123	135	163	184	197	217	230	246
1-alkylnaphthalene										218	240	258	273
1-alkanol	65	78	97	118	138	157	178	195	214	229	246	264	287	296
Alkanoic acid	101	118	142	164	186	202	222	240	256	270	280	296	308			351

Boiling point of hydrocarbons, alcohols and acids, C1-C16, °F
Carbon number	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16
2,2-dimetylalkane					49	121	174	223	271	311
2-methylalkane				11	82	141	194	243	289	333	373	412
2-methylalkene				20	88	144	198	244	293	333
3-methylalkane						146	198	248	291	334	378	414
1-alkene		-155	-54	21	86	146	200	250	297	342	379	415	451	484
N-alkane	-259	-127	-44	31	97	156	209	258	303	345	385	421	456	488	518	549
1-alkyne		-119	-10	47	104	160	212	259	303	345	385	419	453			543
Alkylcyclohexane*							214	270	313	352	399	437	471	505
Alkylcyclopentane						161	219	268	313	356	403	435	468	504	534
Alkylbenzene*						176	231	277	319	361	401	439	468	505
Cycloalkene**			-33	36	112	181	239
Cycloalkane**			-27	55	121	177	246	304	343	396
2-alkanol			180	211	246	280	318	354	380	414	448	480
4-alkanol							322	349	379	417
3-alkanol					253	275	325	363	387	423	445	474
1-alkylnaphthalene										424	464	496	523
1-alkanol	148	173	207	244	280	314	352	382	417	444	475	507	549	564
Alkanoic acid	214	244	287	327	367	396	432	464	493	518	536	565	586			664
* C#(N-alkyl)=0-10
** rings without substituents

Definitions of organic compounds

Hydrocarbon: An organic compound consisting entirely of hydrogen and carbon.

Main groups of hydrocarbons:

Alkane: An acyclic saturated hydrocarbon, with the general formula CnH2n+2. Also called paraffin.

Alkene: An unsaturated hydrocarbon that contains at least one carbon–carbon double bond, with the general formula CnH2n. Also called olefine.

Alkyne: An unsaturated hydrocarbon containing at least one carbon—carbon triple bond, with the general formula CnH2n-2. Also called acetylene.

Cycloalkane: A one-ring (monocyclic) saturated hydrocarbon, with the general formula CnH2n. Also called naphthene.

Cycloalkene: An alkene hydrocarbon which contains a closed ring of carbon atoms, but has no aromatic character, with the general formula CnH2n-2. Also called cycloolefin.

Aromatic hydrocarbon: A cyclic (ring-shaped), planar (flat) molecule with a ring of resonance bonds that exhibits more stability than other geometric or connective arrangements with the same set of atoms. The simplest of the aromatics have 6 carbon atoms and contains 3 double bounds. A one ring aromatic without any substituents is called benzene, with the formula C6H6.

Polycyclic aromatic hydrocarbons: hydrocarbon that are composed of multiple aromatic rings. A two ring aromatic without any substituents is called naphthalene, with the formula C10H8.

Some under-groups of hydrocarbons given in this document:

Alkyl: An alkane substituent missing one hydrogen, with general formula CnH2n+1

2-Methylalkane: A branched alkane, with a methyl group connected to the second carbon atom in the main carbon chain.

3-Methylalkane: A branched alkane, with a methyl group connected to the third carbon atom in the main carbon chain.

2-Methylalkene: A branched alkene, with a methyl group connected to the second carbon atom in the main carbon chain.

Alkylcycklohexane: A monosubstituted cyclohexane with one branching via the attachment of one alkyl group on one carbon of the cyclohexane ring, with the general formula CnH(2n+1)C6H11.

Alkylcycklopentane: A monosubstituted cyclopentane with one branching via the attachment of one alkyl group on one carbon of the cyclohexane ring, with the general formula CnH2n+1C5H9.

Alkylbenzene: A monosubstituted benzene with one branching via the attachment of one alkyl group on one carbon of the benzene ring, with the general formula CnH(2n+1)C6H5.

Alkylnaphthalene: A monosubstituted naphthalene with one branching via the attachment of one alkyl group on one carbon of one of the aromatic rings, with the general formula CnH(2n+1)C10H7.

Some other groups of organic compounds:

Alcohol: an organic compound in which the hydroxyl functional group (–OH) is bound to a saturated carbon atom

Alkanol: An alcohol where the hydroxyl group is connected to an alkane

Carboxylic acid: an organic compound that contains a carboxyl group (C(=O)OH). The general formula of a carboxylic acid is R–COOH, with R referring to the rest of the molecule.

Alkanoic acid: A carboxylic acid where the R is an alkane.

How does number of carbon atoms affect boiling point?

Physical properties The boiling points of alkanes increase with increasing number of carbons. This is because the intermolecular attractive forces, although individually weak, become cumulatively more significant as the number of atoms and electrons in the molecule increases.

Does carboxylic acid increase boiling point?

Carboxylic acids have high boiling points compared to other substances of comparable molar mass. Boiling points increase with molar mass.

What is the cause for the high boiling points of the carboxylic acids?

In a pure carboxylic acid, hydrogen bonding can occur between two molecules of acid to produce a dimer. This immediately doubles the size of the molecule and so increases the van der Waals dispersion forces between one of these dimers and its neighbors - resulting in a high boiling point.

Why does boiling point increase with carbon chain length?

Melting and Boiling Point As the carbon chain gets longer, there are more electrons in a molecule. This means that there are more (relatively) stronger intermolecular forces between the molecules. As a result, it takes more energy to break these forces, and thus the melting or boiling points increase.