5-acetyl-2,3-dihydro-1,4-thiazine

5-acetyl-2,3-dihydro-1,4-thiazine is a sulfur-containing heterocyclic compound characterized by the molecular formula C₆H₉NOS and a molecular weight of approximately 143.21 g/mol. It appears as a colorless to light yellow substance with a distinctive nutty odor reminiscent of cooked roasted popcorn at low concentrations, such as 0.01% in propylene glycol. The compound is also known under various synonyms including 1-(3,4-dihydro-4H-1,4-thiazin-5-yl)ethanone. It is sourced through chemical synthesis commonly for use as a flavoring agent. In flavor and fragrance chemistry, it holds significance due to its sulfur heterocyclic structure, which contributes to its characteristic sensory properties. More detailed chemical and structural information is accessible through controlled-vocabulary databases such as PubChem.

5-acetyl-2,3-dihydro-1,4-thiazine occurs as a synthetic flavoring compound designed to impart nutty and roasted aroma notes. It is applicable in flavor formulations that mimic or enhance the profile of nuts like almond, hazelnut, pecan, and walnut, as well as tropical coconut and spices such as nutmeg and mace. These properties render it useful in various food matrices including baked goods, beverages, snacks, dairy products, and confectionery. Regulatory bodies such as FEMA (US) recognize its general usage under flavoring agents classification. However, its use in fragrance applications is restricted by IFRA (Global) guidelines due to genotoxicity alerts. Overall, its potential lies in flavor enhancement to create creamy, nutty, and roasted sensory impressions within consumer foods.

This compound exhibits melting points between 67 to 69 °C at standard atmospheric pressure, indicating a solid state at room temperature. Its boiling range spans approximately 259 to 319 °C under 760 mm Hg, reflecting moderate thermal stability for volatilization in flavor delivery systems. The experimentally estimated logP value near -0.08 suggests a balanced hydrophilic-lipophilic character, enabling some solubility in both aqueous media and organic solvents. It is soluble in methylene chloride and alcohol, and exhibits moderate water solubility estimated at 361 mg/L at 25 °C. A vapor pressure of 0.002 mm Hg at ambient temperature implies low volatility, thus contributing to prolonged aroma persistence. The relatively high flash point of 264 °C (tested by Tag Closed Cup method) indicates low flammability risk during handling and formulation. Such properties influence its incorporation and stability in diverse product platforms requiring nutty aroma nuances.

	1-(3,4-dihydro-4H-1,4-thiazin-5-yl)ethanone
NIST Chemistry WebBook:	Search Inchi
Pubchem (cid):	526853
Pubchem (sid):	135324865
	1-(3,4-dihydro-2H-1,4-thiazin-6-yl)ethanone
NIST Chemistry WebBook:	Search Inchi
Pubchem (cas):	101417-25-8

(IUPAC):	Atomic Weights of the Elements 2011 (pdf)
Videos:	The Periodic Table of Videos
tgsc:	Atomic Weights use for this web site
(IUPAC):	Periodic Table of the Elements
FDA Substances Added to Food (formerly EAFUS):	View
HMDB (The Human Metabolome Database):	HMDB34882
FooDB:	FDB013457
ChemSpider:	View

Safety information

Hazards identification
Classification of the substance or mixture
GHS Classification in accordance with 29 CFR 1910 (OSHA HCS)
None found.
GHS Label elements, including precautionary statements
Pictogram
Hazard statement(s)
None found.
Precautionary statement(s)
None found.
Oral/Parenteral Toxicity:
Not determined
Dermal Toxicity:
Not determined
Inhalation Toxicity:
Not determined

Safety in use information

Category:
flavoring agents
IFRA fragrance material specification:
	Genotoxic alert
Recommendation for 5-acetyl-2,3-dihydro-1,4-thiazine usage levels up to:
	not for fragrance use.
Maximised Survey-derived Daily Intakes (MSDI-EU):		0.012 (μg/capita/day)
Modified Theoretical Added Maximum Daily Intake (mTAMDI):		4000 (μg/person/day)
Threshold of Concern:		90 (μg/person/day)
Structure Class:		III
Use levels for FEMA GRAS flavoring substances on which the FEMA Expert Panel based its judgments that the substances are generally recognized as safe (GRAS).
The Expert Panel also publishes separate extensive reviews of scientific information on all FEMA GRAS flavoring substances and can be found at FEMA Flavor Ingredient Library
publication number: 23
Click here to view publication 23
		average usual ppm	average maximum ppm
baked goods:		5.00000	20.00000
beverages(nonalcoholic):		1.00000	10.00000
beverages(alcoholic):		2.00000	10.00000
breakfast cereal:		5.00000	20.00000
cheese:		1.00000	5.00000
chewing gum:		-	-
condiments / relishes:		5.00000	25.00000
confectionery froastings:		2.00000	10.00000
egg products:		1.00000	5.00000
fats / oils:		-	-
fish products:		-	-
frozen dairy:		1.00000	5.00000
fruit ices:		-	-
gelatins / puddings:		2.00000	10.00000
granulated sugar:		2.00000	10.00000
gravies:		-	-
hard candy:		2.00000	10.00000
imitation dairy:		2.00000	10.00000
instant coffee / tea:		2.00000	10.00000
jams / jellies:		-	-
meat products:		1.00000	5.00000
milk products:		2.00000	5.00000
nut products:		-	-
other grains:		2.00000	5.00000
poultry:		-	-
processed fruits:		-	-
processed vegetables:		1.00000	5.00000
reconstituted vegetables:		-	-
seasonings / flavors:		50.00000	1000.00000
snack foods:		2.00000	10.00000
soft candy:		2.00000	10.00000
soups:		-	-
sugar substitutes:		10.00000	25.00000
sweet sauces:		-	-
Food categories according to Commission Regulation EC No. 1565/2000 (EC, 2000) in FGE.06 (EFSA, 2002a). According to the Industry the "normal" use is defined as the average of reported usages and "maximum use" is defined as the 95th percentile of reported usages (EFSA, 2002i).
Note: mg/kg = 0.001/1000 = 0.000001 = 1/1000000 = ppm.
		average usage mg/kg	maximum usage mg/kg
Dairy products, excluding products of category 02.0 (01.0):		0.40000	2.00000
Fats and oils, and fat emulsions (type water-in-oil) (02.0):		0.20000	1.00000
Edible ices, including sherbet and sorbet (03.0):		0.40000	2.00000
Processed fruit (04.1):		0.30000	1.50000
Processed vegetables (incl. mushrooms & fungi, roots & tubers, pulses and legumes), and nuts & seeds (04.2):		-	-
Confectionery (05.0):		0.40000	2.00000
Chewing gum (05.3):		-	-
Cereals and cereal products, incl. flours & starches from roots & tubers, pulses & legumes, excluding bakery (06.0):		0.20000	1.00000
Bakery wares (07.0):		0.40000	2.00000
Meat and meat products, including poultry and game (08.0):		0.10000	0.40000
Fish and fish products, including molluscs, crustaceans and echinoderms (MCE) (09.0):		0.10000	0.40000
Eggs and egg products (10.0):		-	-
Sweeteners, including honey (11.0):		-	-
Salts, spices, soups, sauces, salads, protein products, etc. (12.0):		0.20000	1.00000
Foodstuffs intended for particular nutritional uses (13.0):		0.40000	2.00000
Non-alcoholic ("soft") beverages, excl. dairy products (14.1):		0.20000	1.00000
Alcoholic beverages, incl. alcohol-free and low-alcoholic counterparts (14.2):		0.40000	2.00000
Ready-to-eat savouries (15.0):		1.00000	5.00000
Composite foods (e.g. casseroles, meat pies, mincemeat) - foods that could not be placed in categories 01.0 - 15.0 (16.0):		0.20000	1.00000

Safety references

European Food Safety Athority(EFSA):Flavor usage levels; Subacute, Subchronic, Chronic and Carcinogenicity Studies; Developmental / Reproductive Toxicity Studies; Genotoxicity Studies...

European Food Safety Authority (EFSA) reference(s):

Flavouring Group Evaluation 21: Thiazoles, thiophene, thiazoline and thienyl derivatives from chemical group 29. Miscellaneous substances from chemical group 30. (Commission Regulation (EC) No 1565/2000 of 18 July 2000) - Opinion of the Scientific Panel on Food Additives, Flavourings, Processing Aids and Materials in contact with Food (AFC) View page or View pdf

Flavouring Group Evaluation 76, (FGE.76)[1] - Consideration of sulphur-containing heterocyclic compounds evaluated by JECFA (59th meeting) structurally related to thiazoles, thiophene, thiazoline and thienyl derivatives from chemical group 29, miscellaneous substances from chemical group 30 evaluated by EFSA in FGE.21 - Scientific Opinion of the Panel on Food Additives, Flavourings, Processing Aids and Materials in Contact with Food View page or View pdf

Flavouring Group Evaluation 21, Revision 1 (FGE.21Rev1): Thiazoles, thiophene, thiazoline and thienyl derivatives from chemical group 29 Miscellaneous substances from chemical group 30 View page or View pdf

Flavouring Group Evaluation 93 (FGE.93): Consideration of sulphur heterocyclic evaluated by JECFA (68th meeting) structurally related to thiazoles, thiophene, thiazoline and thienyl evaluated by EFSA in FGE.21Rev1 (2009) View page or View pdf

Scientific Opinion on Flavouring Group Evaluation 21, Revision 2 (FGE.21Rev2): Thiazoles, thiophene, thiazoline and thienyl derivatives from chemical group 29. Miscellaneous substances from chemical group 30. View page or View pdf

Scientific Opinion on Flavouring Group Evaluation 21, Revision 3 (FGE.21Rev3): Thiazoles, thiophenes, thiazoline and thienyl derivatives from chemical groups 29 and 30 View page or View pdf

Scientific Opinion on Flavouring Group Evaluation 21, Revision 4 (FGE.21Rev4): Thiazoles, thiophenes, thiazoline and thienyl derivatives from chemical groups 29 and 30 View page or View pdf

Scientific Opinion on Flavouring Group Evaluation 21, Revision 4 (FGE.21Rev4): Thiazoles, thiophenes, thiazoline and thienyl derivatives from chemical groups 29 and 30 View page or View pdf

Scientific Opinion on Flavouring Group Evaluation 21, Revision 5 (FGE.21Rev5): Thiazoles, thiophenes, thiazoline and thienyl derivatives from chemical groups 29 and 30 View page or View pdf

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EPA ACToR:Toxicology Data

EPA Substance Registry Services (SRS):Registry

Laboratory Chemical Safety Summary :526853

National Institute of Allergy and Infectious Diseases:Data

1-(3,4-dihydro-4H-1,4-thiazin-5-yl)ethanone

Chemidplus:0164524930

1-(3,4-dihydro-2H-1,4-thiazin-6-yl)ethanone