The primary difference between tert- and neo- is that neo- originates from an outdated naming system largely discontinued, while tert-butyl is a common name (mixed with IUPAC nomenclature) that remains in use, specifically for substituents.
Here's a more detailed breakdown:
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tert- (tertiary): This prefix indicates that a carbon atom is bonded to three other carbon atoms. It's most commonly used in tert-butyl (or t-butyl), a common and accepted term in organic chemistry. This usage persists even though the IUPAC nomenclature exists.
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neo-: This prefix, meaning "new," was historically used to denote isomers where a carbon atom is bonded to four other carbon atoms (a quaternary carbon), with at least one methyl group attached to the second carbon away from the main chain attachment point. Critically, neo- is generally attached to a pentane or larger structure. The usage of neo- is becoming less common in modern IUPAC nomenclature and is frequently replaced with more systematic naming conventions.
Table Summarizing the Key Differences
| Feature | tert- (Tertiary) | neo- |
|---|---|---|
| Meaning | Indicates a carbon atom bonded to three other carbon atoms. Commonly used for a tert-butyl group. | Refers to an isomer with a quaternary carbon, typically with methyl groups on the second carbon from the attachment point. |
| Common Usage | Still frequently used, particularly for tert-butyl substituents. | Less common in current IUPAC nomenclature; largely replaced by systematic names. |
| Structure Type | Can be used with smaller groups (e.g., tert-butyl). | Generally applied to pentane or larger structures. |
Examples
- tert-butyl alcohol: (CH3)3COH. This is an accepted and common name.
- *neopentane: (CH3)4C. While still used, the IUPAC name 2,2-dimethylpropane is preferred.
Conclusion
While both tert- and neo- are prefixes used in organic chemistry nomenclature, tert- remains a common and accepted part of substituent naming (especially tert-butyl), while neo- is an older term that has largely been superseded by systematic IUPAC naming conventions and tends to apply to larger structures like pentane.
