Estratetraene Chemistry: Position Matters

Overview

Estratetraenes are 18-carbon steroids with four double bonds in the steroid nucleus. The position of these double bonds has profound effects on:

Chemical stability
Biological activity (estrogenic vs non-estrogenic)
Pheromone vs hormone function
Species specificity (human vs equine)

A critical misconception in pheromone communities is that “16-estratetraenone” exists. It does not, and cannot exist for fundamental chemical reasons.

Estrane Backbone

Basic Structure

Estrane (C₁₈H₃₀) is the parent structure of all estrogens:

18 carbon atoms (vs 19 for androstane)
Lacks the C19 methyl group at position 10
A-ring is typically aromatic (3 double bonds)

The loss of C19 is what defines the estrane series.

The “Tetraene” Problem

What “Tetraene” Means

Tetraene = four double bonds (tetra = four, -ene = double bond)

For a steroid to be a tetraene, it must have exactly 4 double bonds in conjugation or specific positions.

The Two Strategies

There are only two chemically stable ways to achieve four double bonds in an estrane:

Strategy	Double Bond Positions	Result
A-ring aromatic + one more	1,3,5(10) + one additional	Most common
Extended conjugation	1,3,5(10),6 or similar	Rare, unstable

Human Estratetraenes: 16-Position

Estra-1,3,5(10),16-tetraen-3-ol

This is the canonical human estratetraene:

Double bonds at positions 1, 3, 5(10), and 16
A-ring is aromatic (positions 1,3,5)
Additional double bond at position 16 (D ring)
Chemically stable
Non-estrogenic (no receptor binding)

Why Position 16?

The 16-position double bond:

Is geometrically isolated from the aromatic A-ring
Creates a reactive site for oxidation/metabolism
Increases volatility dramatically
Does NOT extend conjugation to the A-ring
Chemically feasible

Biological Source

Human estratetraenes with 16-position double bonds are:

Metabolites of estrogen breakdown
Found in urine, sweat
Pheromone-active but not estrogenic
Produced by both sexes (higher in women)

Horse Estratetraenes: 8-Position

Equilin and Equilenin

Horses produce estratetraenes with the fourth double bond at position 6, 7, or 8:

Equilenin: Estra-1,3,5(10),6,8-pentaen-3-ol (actually a pentaene) Equilin: Estra-1,3,5(10),7-tetraen-3-ol

Why Position 7 or 8?

The 7 or 8-position double bond:

Extends conjugation with the aromatic A-ring
Creates a larger aromatic system
Highly estrogenic (binds estrogen receptor)
Used in hormone replacement therapy (Premarin = Pregnant mare urine)

Extended Conjugation

Aromatic A-ring: positions 1,3,5(10)
    + 
7 or 8 position double bond
    = 
Extended conjugated system
    = 
Estrogen receptor binding

This extended conjugation is why equine estrogens are powerfully estrogenic.

The “16-Estratetraenone” Myth

Why It Cannot Exist

Many pheromone vendors list “16-estratetraenone” or similar compounds. This is chemically impossible.

The Problem

To have a molecule called “16-estratetraenone,” you would need:

Four double bonds (tetraene)
A keto group at position 16

But: If there’s a keto group (=O) at position 16, there cannot be a double bond at position 16.

Chemical Reality

Claimed Name	Problem	Reality
16-estratetraenone	Keto at 16 + double bond at 16?	Impossible
Estra-1,3,5(10),16-tetraen-3-ol	✓ Valid	This exists
Estra-1,3,5(10)-trien-16-one	✓ Valid	Only 3 double bonds (triene)

What They Probably Mean

When vendors list “16-estratetraenone,” they likely mean:

Estra-1,3,5(10)-trien-16-one (a triene with keto at 16)
Estra-1,3,5(10),16-tetraen-3-ol (actual tetraene, no keto)
Complete misunderstanding of nomenclature

Human vs Horse Comparison

Feature	Human Estratetraene	Horse Estratetraene
4th double bond	Position 16 (D ring)	Position 7 or 8 (B ring)
Conjugation	A-ring isolated	Extended to B ring
Estrogenic activity	Minimal/none	High
Biological role	Pheromone metabolite	Hormone
Volatility	High (16-position)	Lower
Receptor binding	No ER binding	Strong ER binding

Why Position Matters

Chemical Conjugation

Conjugated system: Alternating single and double bonds that allow electron delocalization.

Positions 1,3,5(10),7: Forms extended conjugated system
Positions 1,3,5(10),16: A-ring isolated, D-ring isolated

Receptor Recognition

The estrogen receptor (ER) recognizes:

Aromatic A-ring (required)
Extended conjugation into B-ring (enhances binding)
Phenolic hydroxyl at position 3 (hydrogen bonding)

Human 16-estratetraenes lack the extended conjugation, so they do not bind ER.

Evolutionary Divergence

Species	Strategy	Purpose
Humans	16-position (non-estrogenic)	Pheromone signaling
Horses	7/8-position (estrogenic)	Reproductive hormone

This may reflect different reproductive strategies and signaling needs.

Volatility Considerations

16-Position Double Bond Effect

The 16-position double bond dramatically increases volatility by:

Reducing molecular weight (loss of H₂)
Increasing rigidity (less surface contact)
Creating reactive site (more favorable evaporation)

Comparison

Molecule	Double Bonds	Relative Volatility
Estrone	3 (aromatic A-ring)	Low
Estra-1,3,5(10),16-tetraen-3-ol	4 (A-ring + 16)	High
Androstenone	1 (position 16)	High

The 16-position double bond is a volatility hotspot regardless of parent structure.

Estrogenic vs Non-Estrogenic

Estrogenic Activity Requirements

For a molecule to be estrogenic, it needs:

Aromatic A-ring (positions 1,3,5(10))
Hydroxyl at position 3 (mimics estradiol)
Extended conjugation or proper D-ring structure
Correct 3D shape for receptor binding

Human Estratetraenes: Non-Estrogenic

Despite having an aromatic A-ring and 3-OH, human estratetraenes are not estrogenic because:

16-position double bond does NOT extend conjugation
D-ring geometry is wrong for receptor binding
Oxidation-prone (metabolically unstable)

Horse Estratetraenes: Estrogenic

Equine estratetraenes ARE estrogenic because:

Extended conjugation from A to B ring
Proper geometry for receptor binding
Metabolically stable

Metabolic Pathways

Human Estrogen Breakdown

Estradiol (E2) → Multiple metabolites, including:

16α-hydroxyestrone
16-oxoestradiol
Estra-1,3,5(10),16-tetraenes (via dehydration)

The 16-estratetraenes are terminal metabolites with pheromone function.

Why This Matters

Human estrogen metabolites are designed to:

Signal reproductive status
Not re-activate estrogen receptor (avoid positive feedback)
Remain volatile for pheromone diffusion

Analytical Chemistry Issues

Misidentification

Many studies and vendors confuse:

Estra-1,3,5(10),16-tetraen-3-ol (correct)
“16-estratetraenone” (impossible)
Estra-1,3,5(10)-trien-16-one (triene, not tetraene)

Mass Spectrometry

Compound	Molecular Formula	m/z
Estra-1,3,5(10),16-tetraen-3-ol	C₁₈H₂₀O	252
Estra-1,3,5(10)-trien-16-one	C₁₈H₂₂O₂	270

These are different molecules with different properties.

Practical Implications

For Pheromone Products

Verify nomenclature: “16-estratetraenone” is a red flag
Check analytical data: Mass spec should match claimed structure
Understand source: Human vs equine origin matters
Estrogenic risk: True estratetraenes (16-position) are non-estrogenic

For Users

Concern	Human 16-Estratetraenes	Horse 7/8-Estratetraenes
Estrogenic effects	None	High risk
Pheromone activity	Yes	Limited
Safety	Safe	Hormone exposure

Copulin Confusion

”Estratetraenol” Claims

Some products claim “estratetraenol” (note: -ol suffix = hydroxyl) is a “copulin.”

Reality:

Copulins are short-chain fatty acids (acetic, propionic, butyric, etc.)
Estratetraenes are steroid metabolites
These are completely different compound classes

Marketing vs Chemistry

Marketing Term	Chemical Reality
”Female copulin blend”	Might contain estratetraenes OR fatty acids
”Estratetraenol”	Likely estra-1,3,5(10),16-tetraen-3-ol
”16-estratetraenone”	Doesn’t exist; misnamed compound

Chemical Stability

Why 16-Position Works

The 16-position double bond is:

Isolated from A-ring (no competing conjugation)
Geometrically accessible (D-ring is small)
Metabolically produced (enzyme-catalyzed)

Why 7/8-Position Is Rare in Humans

Humans lack enzymes to efficiently create 7 or 8-position double bonds in estrane because:

Evolution favored non-estrogenic pheromones
Estrogenic metabolites would interfere with hormonal regulation
16-position serves pheromone function better

Key Takeaways

Estra-1,3,5(10),16-tetraen-3-ol is the human estratetraene (16-position)
“16-estratetraenone” cannot exist (keto + double bond at same position is impossible)
Horse estratetraenes have 7 or 8-position double bonds (estrogenic)
Human estratetraenes are non-estrogenic (no receptor binding)
16-position double bond increases volatility (pheromone function)
Extended conjugation determines estrogenic activity (7/8-position)
Verify product nomenclature (many vendors get this wrong)

Scientific Confidence

Confidence Level: High

The chemistry described here is fundamental organic chemistry and well-established steroid biochemistry. The impossibility of “16-estratetraenone” is unambiguous. The difference between human and equine estrogen metabolites is confirmed by extensive literature.

The main uncertainty is in the pheromone effects of estratetraenes, which are less studied than androstanes.